You don't need most of the stuff on a bike. That's no justification, though, for not building something new.
With every new product, there's always some group, stuck in their ways, that can't help but say, "That is necessary." ****, nearly everything we see around is in life isn't necessary.
There's more than talk:
Campy's already made the announcement; it's on their website; and it's being used in the Tour d'ASO.
I can't remember if the freehub is not compatible with 10 spd, but I think the answer is "no." You will not be able to run 11 spd cassettes in a 10 spd system. The shifters are also completely different, but whether or not Ultra shifters can be modded to accept 11 spd, no one knows yet. You'll still be able to use your compact crank, but you might need the new chainrings since the new 11 spd chain is narrower than the 10 spd. It's said that the 10 spd chain won't work with 11 spd because of the narrower spacing in the rear.