Ofc i would play, but reasonable end game progression would suffer greatly if they leave some raids and dungeons as they were in 1.12, and i mean mainly Dire Maul and Zul'Gurub, which were meant to be kind of catch-up content for latecomers and/or incompetent players.
If all raids and dungeons are released at once, all level 60 dungeons and raids should be retuned to maintain natural progression curve.