CasualWandumvalve doesnt really have a reason
thats why they're not doing it
There was no 'reason' to make team fortress 2 in the first place, either.
the engine with this art style, all they gotta do is let us unlock the picmap and we get really nice textures. They can always go back and work on models, fix the code, cosmetic glitches, bugs, exploits. They can balance and add more weapons, they do whatever they want really.
the big thing is the folks using third party programs to cheat at this game. thats the problem. we dont need a new game, we need to handle the cheaters.