Would you keep Thor:Ragnarok and Black Panther in theaters until Avengers Infinity War?
If I were Marvel/Disney I would leave both Thor and Black Panther in theaters until Avengers Infinity War. I think both are perfect lead-up films (naturally) and will allow for some audiences to get a bit of background prior to Infinity War.
People are enthusiastic for A:IW but there are many, many potential movie-goers who will just be overwhelmed about the on-goings for this film and will probably avoid it altogether because trying to get fully caught up is too confusing and too daunting.
No theater chain is going to do a 17-20 movie Marathon prior to Infinity War. Some Youtubers are cleverly doing an MCU film per week review (starting at IM1) to get YouTube clicks and honestly that makes a certain amount of sense for neophytes even though there is bias associated with that.
Even though Thor Ragnarok will be out on Blu-Ray March 6th I'd have it in theaters also up to and maybe including A:IW.