Ryan Reynolds has cast doubt on the chances of Deadpool joining either the Avengers or the X-Men, saying being a part of either team would mean the character was "at the end."

Ryan Reynolds speaks on whether fans can expect Wade Wilson / Deadpool in Avengers Doomsday and Avengers: Secret Wars.

That makes a ton of sense. There's seemingly nowhere to go if Deadpool actually becomes an Avenger. Whether or not this prevents him from actually joining Avengers: Doomsday or Secret Wars remains to be seen, but if a crossover happens he likely won't actually become a member of any of the big teams.