I think you are all just overreacting. There's plenty of characters that have been brought back after being gone for many years like Illyana, Kraven, and Vision. Heck, Vision has even had replacements yet that didn't stop him from coming back. Marvel never trolled these guys and I doubt they want to get rid of Jean forever either. Even Tom Brevoort said she may very well come back in the future. The reason why Jean hasn't been brought back yet probably has to do with complications in the current Phoenix/Hope plot.

I think all this doom preaching over Jean having to come back in AvX is simply overinflating Jean's importance to the MU. She does not have to be brought back in a massive company crossover, she's just like any other X-Man and all she needs is a simple story arc at the right oppurtunity.