They've basically already done the biggest event they could (apart from Secret Wars). Would love to see them do something like Dark Reign, and a Thunderbolts movie being set up in the Falcon & Winter Soldier series has been rumoured fo a while now. From now on I'd rather the solo films be like Winter Soldier, Civil War, Spider-Man 2 and Dr Strange 2 and be like mini-Avengers crossover films.
There's been rumours that Black Panther 2 will be based on Doomwar which would be cool but tbh Dr Doom totally deserves his own film. Same with Thanos.