Thanks to the Thunderbolts* post-credits scene, we'd all assumed we knew how The Fantastic Four: First Steps was going to end; with Marvel's First Family having hopped on a ship and travelling, somehow, to Earth-616 on the Sacred Timeline. You know, the universe in which the Avengers exist...

The post-credits scenes of Fantastic Four: First Steps and Thunderbolts are not directly connected. However, it could point towards what we could see in Avengers: Doomsday. There's a chance that the post-credit scene of Fantastic Four: First Steps kicks off Avengers: Doomsday, as Doom might kidnap Franklin and escape to Earth 616.