Koeman reckoned to only be there for one season and then Xavier Hernandez will return from Qatar and take over.He can take another run at the CL for the next two years at City then head back to Barca after Koeman did all the hardwork of moving out the crap and losing (well for Barca standards) as the hero returning.
A lot of the issues at Barca should be fixed by then and they shouldn't have enough success that it won't be easy to move Koeman out so Pep can go back, bring them back to success and keep up his reputation as well.