A war between Earth-838 and Earth-616 could be interesting (spoilers)
As people have mentioned, with Wanda killing the leaders of the X-Men, Inhumans and Fantastic Four - but leaving Mordo alive to tell the tale - this could lead to Earth-838 launching a retaliatory attack on Earth-616.
Perhaps this is how Marvel will integrate all the characters previously owned by 20th Century Fox, by having an "X-Men vs. Avengers"-style scenario that culminates in the two Earths being combined and history rewritten as if these characters (and signature geographical locations like Genosha, the Savage Lands, New Attilan, the Baxter Building, etc) had always co-existed.