If there are legal reasons behind Cox, Bennet, or any number of TV actors appearing as their characters on the big screen, Marvel Studios could always recast these roles to bring them to the big screen.
Feige has previously gone on record saying a true crossover like this is really the subject of timing thanks to how difficult it is to line up productions and story arcs.
This is less than ideal for fans of the small screen iterations and could almost feel unfair to those that made the characters beloved to begin with.
Most importantly however, this continues to show a willingness to make it happen, which is all fans can ask for – even if it requires a longer wait than desired.