There are simply so many moving parts that it’s nearly impossible to get the schedules of the two things in the proper sync.
First and foremost there’s the Marvel movie vs TV problem that has thus far kept any of the members of Marvel’s television series out of the movies.
Add to that the fact that the two entities are run through different chains of command, and it’s entirely possible that we’ll never see a Marvel TV character in the movies.
As James Gunn says in his tweet, maybe they should just do something else, because Kingpin vs Baby Groot is just about the least likely MCU crossover to ever happen.