[Update]
A new image has been revealed by the Overwatch twitter account today. The image shows a "prototype biotic rifle" blueprint that is based on Mercy's Caduceus Staff accompanied by statements from Torbjorn and Mercy talking about the development and potential use for the "biotic rifle". The blueprint also shows what appears to be a piece of equipment or grenade that is based off of Soldier: 76's Biotic Field ability. The rifle's scope looks identical to the scope that was seen being worked on spotted in the Gamespot video cited below. With the prevailing rumors being that Sombra will be a support sniper hero, the "biotic rifle" makes Sombra's reveal all the more anticipated. Blizzard has not made any statement on the image, so unfortunately there is still no official word on when Sombra will be released, but it has become an almost certainty that Sombra will be the first new hero released. (There is also an image floating around apparently taken from an initial post made by the Spanish Overwatch Facebook account that included "A.Amari" with "J.Morrison" and "G.Reyes" at the top left of the image, no confirmation on whether the image is legitimate or a photoshopped image.)
Recently Blizzard announced a new Overwatch animated short featuring Solider 76, after this a French chain of theaters put together a teaser image for th announcement. On the announcement, the words "Nouveau Heros" can be seen which translates to "new heroes". After doing some digging, and the help of Neogaf user "Nirolak", there seems to be one hero in particular that all the clues are pointing to as being the new hero. Surprising no one, the theater claims this was a terrible typo accident.
All clues point to "Sombra" being the new hero to be revealed, based on physical evidence as well as her place in Overwatch lore. Now trying to pin down info on the new character has to start with Blizzard themselves, and they have said they are working on new heroes, but other than that they've not given any "official" details. However, they have put in lots of hints and teases into Overwatch itself as well as in the "The Story Of Overwatch" videos that GameSpot recently released. Before we dive deep into speculation territory this is a reminder that you should take all of this with a grain of salt, the theater could very well be telling the truth and there might be not new hero reveal this coming Monday.
First, we'll start with the in-game evidence for Sombra being the new hero. The new Solider 76 short coming out is going to take place on the Dorado map; some players exploring the level noticed "classified" documents on a table in the level mentioning Solider 76 and Jack Morrison (Solider 76's real identity), and there was also a file for Sombra. This could mean that we will see Sombra or here mention of her in the upcoming short. It should be noted Blizzard has teased soon to be released heroes like this in the past, such as with D.Va.
Another photo in a newspaper shows a hooded figure from behind with the title of the article being "¿Quién Sombra?". The newspaper also features pictures of the festival decorations found on the Dorado map.
Route 66 also has a file on a table featuring a hooded masked figure with a photo of the Lumerico building from the Dorado map. Other in-game evidence comes from Reaper who has a dialog line saying "Where is Sombra when you need her?". This seems to suggest that she and Reaper have a history or at the very least are "villain" heroes that work together.
Recently when teasing the Solider 76 short, Blizzard released a new photo of the Lumerico building, and if you zoom in at the top of a building at the bottom middle of the Lumerico building you can make out what appears to be Sombra overlooking Dorado.
Secondly, the GameSpot video has shots that include developer computer screens that give us a hint at what they are working on. At the 10 second mark, we can see what looks like a gun scope where the reticle design is the same as Sombra's mask. We then see what appears to be Sombra herself being chosen on the character select screen, it shows what looks like a hooded figure with some blue coloring, this could also just be an unreleased skin for Widowmaker as the character seems to be using Widowmaker's model stance.
In terms of where Sombra would most likely fit into the lore of Overwatch comes hinges on if she is featured in the Solider 76 short. The inclusion of Sombra with the Solider 76 files on the table on Dorado suggests they're involved with each other in some way and Reaper's dialog line about knowing her might suggest that she was a member of the original Overwatch organization. This has lead to the belief that Sombra is Pharah's mom, Ana Amari. Ana Amari was part of the original team as a sniper and is believed to be dead, but two other Overwatch heroes, Solider 76 and Reaper, were original members who are believed to be dead as well.
As is stands now if we are going to see a new hero revealed, it has a high probability of being Sombra, and Sombra herself might just be Pharah's mom. Of course, all of this could be completely wrong and we could get no new hero at all, or it might be someone completely different, the only way to find out for sure is to wait until Monday.
