Although of course such a film is yet to be officially confirmed, would that be a good idea? Presumably Vader would be searching for Obi-Wan at some point after the end of ROTS; sort of part of his job, anyway-and Obi-Wan, in some way, would be given the confirmation of the fate of his former apprentice.
Not that they would have to meet again or anything, as that would kind of hurt the original film's reunion. Maybe a 'close call' of sorts. Vader of course had a role in "Rogue One" with not really meeting any of the heroes, although he did have sort of an impact on the story leading into the first film.