Current day Ubisoft would likely destroy the franchise if another one was approved for development. The games on XBOX and 360 were all great fun, but...
They've destroyed Ghost Recon, made Rainbow Six into a "game as a service" model with silly hero characters akin to every other mediocre copy and paste cartoony arena shooter, Assassins Creed is basically Madden with swords released on a yearly basis with new skins, and then there's Immortals which is basically Zelda lite.
They "destroyed" Ghost Recon if you want it to be a milsim, but at that point you may as well just play Arma 3. Which has pretty much been the king for a long time anyways for the genre.
The Tom Clancy videogame brand hasn't been about milsim in over a decade anyways so what they've done with Ghost Recon/Rainbow Six has just been an evolution of their style. I really enjoy what they did with Ghost Recon, and it's open world co-op is a blast. They really did a great job at improving Breakpoint as well after it's rough launch. I think you make a fair point about Rainbow Six: Siege, but on it's own merits it's a really fun MP game. Though I vastly enjoyed the R6 as a way of playing co-op against PC, we'll have games soon enough to fill that void that Ubi kind of left on the table. But I would still say that both of those franchises are still really fun, even if they've evolved pretty drastically since their inception.
They could make a good Splinter Cell if they really wanted, and even if it were to release and it's not exactly what people want, Ubisoft had an incredible track record of sticking with their titles very long term to make massive improvements in regards to criticism.
