If I was a betting man, I think Hickman will return Crystal to the team with Ronan the Accuser.
I think he will also indroducing a couple brand new, never seen heroes as well. a new Swordsman perhaps?
as for people who have NEVER been on the Avengers? Heres a list of candidates that may make sense.
Human Torch II
Beta Ray Bill
Lyra the Savage She-Hulk
Shang-Chi (already announced)
Nick Fury (probably a lock)
Hopefully we will not see any more Red Hulk, Red She-Hulk, X-23, Spider-Girl or A-Bomb. I hate rip off characters for the most part.
Who would I like to see return to the fold?
Starfox (c'mon...Thanos is back baby!)
Wasp (resurrect her already!)
I'd just like to be suprised. I respect Hickman a great deal and greatly admired his work on Secret Warriors and Fantastic 4 but its been a very long time since Marvel did anything that made me raise an eyebrow so heres hoping.
I'd like to see a team that makes sense most of all rather than just cramming the most common heroes together or the heroes which are the best in their particular fields.