Universal Studios has a contract that pre-dates Disney's acquisition of Marvel. In that contract there is a 'no compete' clause, guaranteeing Marvel cannot sell the rights to create rides/attractions or have character appearances within so many miles of US's Islands of Adventure. That contract would include even themselves (aka Disney).
Disneyland actually has featured characters from the Marvel Cinematic Universe at their park. Eventually Disney Corporate will have to decide if they wish to renew Universal Studio's contract and at what price or take back the rights for themselves. I believe I read somewhere the current contract was scheduled to expire in 2020.