Is the gameplay significantly changed? From what I've seen of the features, it hasn't really changed from a base gameplay perspective.
Really, if you enjoy WoW now then of course you'll enjoy MoP. Perhaps some are not playing because the lack of updated content but they still like the game in general. Those folk will return and like it. Those, such as myself, that were ok with the game but grew tired of that type of gameplay won't really find MoP that enticing. Those that hated WoW won't suddenly like it now, that's a given.