There are a whole lot of people who do not want to lose that shared history, which has been reinforced canon since forever.
Not all of us want to get down the path of hideous grav tanks and suspect 'new' lore.
There are several issues with ranged units (guns, not indirect like bows) in the current Total War Warhammer game. They have tried a few things to address it, such as allowing the first few feet to be uhh not there, or at one point comically allowing you to just flat out shoot through allied units with zero penalty.
I'm hopeful that the new game engine improves things. We are looking at an alpha here after all.
Extremely unlikely. Fantasy was dead remember, TOW and timing around that is what would almost certainly have driven the development of Cathay in both lines. We don't have Kislev miniatures either.
40K is very much alive, very much the flagship, and the kits are there to be tied into. Any new factions will come with Models as well.
That unit coming down the ramp sure looks like a 'skirmish' loose formation from TW Warhammer on Ultra or something size limit.
What was that quote from Curze again?
EDIT: Come on @TheVoidDragon you can practically see the box that would have been dragged out to set them in that formation you have to admit that! :D