From a purely financial perspective, they SHOULD continue to focus on marketplace dominance via STEAM. Whatever game is made for HL3/TF3 will ultimately fail to meet fan expectations (Duke Nukem anyone?).
If the reddit rumors are believed to be true, the former leads of DotA (Icefrog?) and TF2 (Robin Walker) are heavily involved in it's development.
It will need to do something very fresh if it wants to compete.
Valorant felt extremely fresh and slick compared to both CSGO and Overwatch while fitting nicely inbetween. They brought innovation and UX improvements to the format that even CSGO ended up copying after it had been resting on it's laurels for too long.
They have however refocused on cash-cow live-service games rather than the polished single player experiences they were originally famous for. In the 13 years since Portal 2 they've only released one single player game, and that one was driven by their company-wide VR push more than anything else. It's harder to get excited about their games when they no longer want to make anything that can't be leveraged into an infinite money siphon.
They've also had an uptick in disastrous flops with Artifact and Underlords, hopefully Deadlock will be a return to form.
I certainly think Deadlocks ui is unfinished, but the gameplay is certainly something that hasn't been done super well.
I don't love deadlock yet but haven't played it much. Plus, my opinion means nothing, I thought Artifact was a great game.
Deadlock is more like a moba shooter.
(That’s not a bad thing but first-person MOBAs have fallen from favor a bit… which I suppose does leave a market gap.)