Can the Scarlet Witch be the last hope of Marvel and DC having a cross-over? Yes there might be other heroes/villains involved with the crossover but she and Green Lantern are the ones who manage to stop the merging of the two worlds. This would bring along a lot of heroes and some villains who have not yet been featured in any show/movie/credit scene. That and it would be a good thing to have the crossover after a much needed Green Lantern reboot, Avengers 3, JLA, and another two X-Men movies.
Another thing would be the credit scene for the movie, maybe one of Krona's forces trying to negotiate a plan with Ultron, sorta make the fans go like: WTF he died its been a few years and all of the sudden he's back. Maybe have ultron sitting in a chair with Doomsday sitting next to him on the right and Lobo to the left. To make things crazier it should be on Krane's ship and Magneto's helmet on the table.