Soon!
Nova
Did anything Nova related get announced in San Diego?
No, and even uf they have something planned I doubt they'll announce anything before GotG vol 3.
annihilation 2
I don't see Dick harboring to the same dock twice.
No, being Nova is suffering.
Didn’t Thanos BTFO the Xandarians?
Xandar has been destroyed five times now. They can say Xandar survived thanos's attack and got Nova force to strengthen their centurions.
When did 4 and 5 happen? I know the new Novas got killed off screen in Cates' GotG, but I don't count that since they were essentially fanboys of the old ones acting as mall cops.
You shouldn't count that anyway since it wasn't Xandar, but the new base (whose name I forgot). Not like it matters, Cates doesn't follow continuity.
Last time something called "Xandar" was destroyed was when Worldmind took over Ego the Living Planet and used him as a launchpad to recruit hundreds of intelligent species against their will into the Nova Corps. It didn't take, obviously.