It's such a great hybrid genre. If it's just an FPS I won't even get it; I love the Halo series, but I've never beaten a single game because they're so boring. Picture it playing a little more like Mass Effect or Deus Ex.
the rpg genre doesnt fit halo at all. there was rumor of one being in the works, but i believe it was scrapped. transtioning from an fps into an fps rpg... awkward to say the least. plus it just waters down both concepts into well... mass effect. great story... dull gameplay.