In PVP, the event following Captain Marvel has been revealed to be Loki. Based on the placement rewards for that event, it looks like the PVP following Loki will be Human Torch.
In PVE, the next event after Strange Sights will be Deadpool Vs. MPQ. The required characters will be Sandman, Doc Ock, and 2* Steve Rogers. Based on the placement rewards, the essential characters for the following event will be Iceman, 3* Bullseye, and 2* Captain Marvel.