I disagree. The Moira-related retcons were a massive rewrite of X-Men history. Yes, it's still technically "616", but it's not a continuation of the X-Men narrative as written before. Hickman has started a new narrative.
I think you'll be surprised. Polyamory fits with Hickman's high-concept theme of mutants as post-human and creating a new society. Also, aside from Perlmutter, Marvel (editorial in particular) is staffed by progressive hipsters. Poly isn't something that's going to bother them in the slightest.So I dont expect any truly exploration of poly that isn't a infantile *wink wink tease tease*. it's pretty obvious that Marvel won't let him do it
At any rate, we'll find out in the new Giant-Size X-Men #1.