Some of the heroes of Overwatch including potential new heroes Athena (the android figure left of centre) and a red androidBlizzard
For the past few weeks, speculation regarding Overwatch's next playable hero has been hard to avoid. After the long-drawn-out ARG that led to the reveal of Sombra in November, attention inevitably turned to who would be next.
The common wisdom was that the long-teased Doomfist would be a reality. The character was first referenced in the announcement trailer for Overwatch back in 2014, and more recently actor Terry Crews has been making a lot of noise about wanting to play him.
This suggests Doomfist is out, so who will be the game's 24th character? Let's take a walk through the possibilities, and some that may even end up being the 25th, 26th, or 27th hero.Then, on 17 February, the game's director Jeff Kaplan threw a spanner in the works, writing on the game's forum: "24 is not who you think it is."

Efi Oladele

This one came out of the blue earlier this week (21 February), and it is clear there is something going on with Oladele. Blizzard published an "in-lore" interview with the brand new character – a robotic inventor – leading many to think she may be the new hero.
Kaplan has confirmed to Polygon however that this won't be the case (which we assumed given the character is 11-years-old), but he did confirm that Efi will play a part in the story of the new character. In the aforementioned interview, she is asked what she would do with money from a "genius grant" she just won for her work. "Oh... I have an idea," she says.
The common theory is Oladele is working on a robot she could control remotely. The game needs a new tank to fill a similar role as Reinhardt right now, so a hulking robot makes sense. Overwatch's pre-release assets may offer some supporting evidence.
In the Recall animated short, when Winston reactivated the Overwatch programme, a Robotic face flies by...
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An unnamed red robot character spotted in the Recall animated shortBlizzard
In early artwork for the game, you can see the same robot standing behind more familiar heroes...
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The same character in early artwork for OverwatchBlizzard
There is obviously something going on here, so the question is probably closer to "when", rather than "if". Blizzard is known for throwing out false leads, but it is no mistake this new character was introduced into the world at the time when people are expecting news.

Liao

It seems likely Liao is going to turn up in the Overwatch universe somewhere, but at the same time, we also know basically nothing about the character.
Liao is a founding member of the Overwatch, a fact confirmed in an in-universe blog post. Beyond that, they are an unknown. We do not know their first name, country of origin or role within the organisation.
A scrapped graphic novel titled Overwatch: First Strike, which would have focused on the very early days of the team, may have shed some light. Sadly, the comic was cancelled in November due to the story team wanting to "go in a different direction".
There is one unknown character depicted on the would-be graphic novel's cover, leading many to wonder if it could be Liao.
Overwatch Liao First Strike
The character on the cover of First Strike who may be LiaoBlizzard

Athena

Athena is already in Overwatch and her presence is felt every game. She is the announcer counting you into a fight and informing players about the state of objectives.
She featured in the animated short Recall, where we learnt she hangs out with Winston at Watchpoint: Gibraltar. She also exists in the Orca, the Overwatch dropship which acts as a spawn point on some maps, where she briefs teams on their missions.
There are a few hints at the character becoming playable too. Athena's logo is an "A" which is scattered around the Overwatch universe when she is present. That symbol looks very similar to this one on this robotic character which comes from a pre-release asset.
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Athena in early artwork for OverwatchBlizzard
Speaking to PCGamesN recently, Overwatch story mastermind Michael Chu seemed to leave open the possibility of Athena eventually becoming playable, saying: "From the beginning we had this idea that we wanted the announcer to be a character not just the random voice of god.
"We really wanted her to be a character, and so the first way that we were able to evidence that was in the Recall short – and yeah, that's where she is... right now."
None of this suggests Athena will become a playable character soon and it might be quite odd if the announcer of the game was also on the battlefield. Still, there are certainly hints here.

Brigitte

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Brigitte on the right, next to her pal ReinhardtBlizzard
Brigitte is a character of growing repute in the Overwatch lore. She was most prominent in the Dragon Slayer comic where she was introduced as Reinhardt's travelling companion.
She has been mentioned in game as well. When Mercy and Reinhardt are on the same team, Mercy has been known to say: "Reinhardt, I don't approve of you dragging that on your adventures." To which he replies: "Brigitte has made her choice. I would have her at my side."
It is not impossible to envision Brigitte working as a support character. It is clear there is some sort of plan for her.

"Greek"

This is a newer theory and it has been doing the rounds specifically since Kaplan hinted that Doomfist might not be the next hero.
This started with actor Alex Malaos putting on his CV that he had a role in Overwatch (archived here), which he listed simply as "Greek". This is a little shaky since the actor has since told YouTuber TheKingFenrir that the role he played was more background work.
He said: "I was just saying random background lines. You know, like stuff you would hear on a walkie-talkie or from a random secondary character. I've no idea about how they intend to use that if they decide to ever use it."
However, this story is not dead yet. The idea of a "random" secondary character or "walkie talkie stuff" does not sound like something that would be in the game on its own, meaning that this voice work may well be for a future animated short, one that may introduce a new hero.
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The setting of one of Overwatch's three maps set in GreeceBlizzard
There is a little more to this story too. Thus far, every map in the game is tied to one or two characters, with the exception of Ilios, in Greece. This might suggest a character originating from the country is imminent.

Doomfist (Kind Of)

Hear us out.
Kaplan could be throwing out a red herring for the community to chew on, just to take the spotlight off Doomfist. I do not expect that to happen, but nonetheless, what if Doomfist is still imminent, but not set to be the next hero. What if we are to get two at the same time, and he is the 25th?
There is clearly something going on with Doomfist at the moment. Besides all the rumours around the character, there is evidence, such as the Doomfist gauntlet being tampered with on the game's test server.
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The Doomfist posters as seen in Overwatch's Numbani mapBlizzard
Many have speculated that this might be a remnant of a cinematic that is about to drop, for which there is a precedent. On the Hanamura map there is an arrow and lantern that were added after the "Dragons" animated short hit, which are torn in the same place – as seen in the short.
So, perhaps in an upcoming cinematic, someone is trying to get to Doomfist's gauntlet on the Numbai map, smashing that glass and leading to the introduction of Doomfist himself, or another character. Add that Jeff Kaplan has said that there are "multiple new heroes being worked on" in the forums, and there might be something here.

These are just six heroes that could be coming to Overwatch as number 24 (or 25). There are other characters in the Overwatch universe who could make the jump too, including Soundquake, who was mentioned in the announcement short, or Hakim, who showed up trying to complete a contract on Ana in the Old Soldiers comic.
Or, it could be someone completely new.
With Season 3 of the competitive side of Overwatch coming to an end, it seems an announcement may arrive in a matter of days rather than weeks, so hopefully we will find out soon.