I wouldn't be surprised if it was a Forever-like update to add whatever auxillary features they have developed for Shootmania to Trackmania as well, and get the engine up to date with improvements they made for Shootmania (meaning not much new Trackmania-specific content).
But maybe I'm underestimating Nadeo again and they can work on 2 big things at the same time. I don't know, we will see

also, of course I have to fulfil my traditional role of tm-forum pessimist here