Check out these PTR sound files:
https://www.reddit.com/r/Overwatch/c..._ptr/?sort=new
These files were posted more than a month ago, so many more may exist by now. Many of the character lines mention things like "New hero levels", "New advancements discovered", and "New gear." It all points to unlockables for heroes that actually influence their stats / abilities.
If that wasn't enough, the recent Sombra ARG also seems to be hinting at a new game mode. At the momentincrime website, you'll see that Sombra is transmitting information to all active omnics.
You know who else wanted to gain access to all active omnics? The Anubis A.I. in the Pharah comic, the Anubis A.I. planned on seizing control of omnics to use them for military operations, and that appears to be what Sombra is doing as well. In Pharah's comic, Pharah nearly destroyed the entire Anubis facility, but left some of the structure intact to save an ally. So remnants of the Anubis A.I. still exist.
In Soldier 76's comic, you'll see mention of Sombra at an Egyptian compound, close to where the Anubis Facility was located in Pharah's comic. This suggests that Sombra (and Reaper, Soldier 76 hears his voice through the ear piece) has involvement in the aftermath of the Anubis incident. She very likely was tasked with extracting the Anubis code from the remains of the Anubis Facility, and re-engineering it for Talon's purposes in what's now called the Sombra Protocol.
In the Dorado map, we see Sombra Protocol on many of the monitors. Now why would we see mention of Sombra at a Lumerico power plant? Maybe because she's working with them, and plans on using their facilities to power the omnic horde at her disposal. That would explain why she's protecting Lumerico assets on the control terminals in the building, denying access to unauthorized users. Not only that, but Lumerico would also benefit by teaming up with Talon. Lumerico would have struck a very lucrative business deal to supply power to Talon's massive omnic army.
In the Overwatch Cinematic Trailer, we know that Reaper and Widowmaker attempt to steal Doomfist's Gauntlet. But why would they want to steal his gauntlet? Shouldn't Doomfist already have a gauntlet? Well, we see the two kids talking about how Winston beat Doomfist in a fight. This could mean that the Doomfist Winston beat was stripped of his gauntlet and imprisoned, and that he was likely an enemy of Overwatch. The fact that Widowmaker and Reaper tried to retrieve his weapon also suggests that Talon is an ally of Doomfist, and is attempting to restore Doomfist's weapon to him (or to a successor).
So why is Doomfist important regarding Sombra? Because Doomfist's biography states that he sought to undermine the peace between the omnics and humans in Numbani, which would tie in with Talon's goal of starting an omnic war and controlling them using the Sombra Protocol!
In the Alive animated short, we see Widowmaker assassinating Mondatta, an omnic monk who advocated peace between humans and omnics. Now why would Widowmaker be tasked with killing the figurehead responsible for the peace between humans and omnics? Because Talon wanted to start the second omnic crisis! Talon would use the war as a scapegoat to use the Sombra protocol to control all the omnics. The world would believe that the omnics' motive for fighting was due to Mondatta's assassination, but secretly they would be controlled by Talon and serving its interests!
In the Recall animated short, we see Reaper attempting to extract the Overwatch hero database from Watchpoint: Gibraltar. Now why would he be doing that? We know he's been tracking down and eliminating former Overwatch agents from his biography, and having a list of their locations would make it a lot easier to do that.
But Reaper didn't only appear by himself to eliminate Winston / hack the database. Talon operatives accompanied him! Which means Talon had its own reasons for wanting the Overwatch database as well! So who else might have wanted to steal all the data Gibraltar contained on the Overwatch agents? Sombra must have! But why?
Let's think about Sombra's favorite repeated quote:
She who has the information has the power.
Who might be the "she" that has the information? Gibraltar's Athena! Sombra likely identified Athena as a powerful threat to her plans because Sombra knew the only force in the world capable of stopping her omnic army was Overwatch, and Athena had the capability to reunite its members. Successful extraction of the Overwatch hero database would have allowed Talon to hunt down every former Overwatch operative individually and without much resistance.
But because Talon was unsuccessful in its attempt to steal the data necessary to exterminate the ex-Overwatch members one by one, Talon must now contend with an organized Overwatch team once it mobilizes its omnic army. The Overwatch team will be Earth's only hope at stopping Talon's horde of omnics, and that's where we'll come in, when the new game mode launches!