Do you think Marvel Phase 4 will lead to Secret Wars?
I agree, the Secret Wars arc from 1984 will be an awesome big screen adaption, however, I think it is still too soon.
The next big threat will most likely be Secret Invasion. It was announced at SDCC 2017 that the Captain Marvel movie will feature the Skrulls as the antagonists of the film. This could be Marvel setting up the Invasion as the next big crossover event and the Skrulls as the big bad villains would live up to Infinity War's Thanos.