In PVE, the next Story event will be Strange Sights. This event will mark Archangel’s first turn as the essential 5*. The other essential characters this event will be Cloak & Dagger, Blade, and Human Torch. The placement rewards (and expected essentials for the next event) will be 4* Deadpool, Beast, and Storm.
In PVP the events for the off-season will be Black Vortex (with a blue Rocket & Groot at 900) and Best Friends Forever (with a red Rogue at 900). They’ve also announced a few new boosted characters for Best Friends Forever: Star-Lord (Awesome Mix Volume 2), Yondu, Black Bolt, Lockjaw, and Cloak & Dagger.