There have been a couple of Marvel vs. DC crossovers. It's been seven years since the last one. Now, while this is no confirmation, it is possible for another Marvel vs. DC crossover.
While at Comic-Con, recently promoted C.B. Cebulski was asked at the Marvel Mondo Panel on Thursday if we can expect a Marvel vs. DC Crossover in the future. Cebulski's answered for the panel by stating that Marvel would be more than willing to do it again, and that the ball is in DC's court. He then tasked the room to extend that challenge back out to DC in Marvel's name. DC has yet to respond.
Could we actually see another Marvel vs. DC event?