Heard from the 343 Sparkast #12 (sometime around 30 minutes in) podcast. There will be a new(old) weapon in the game formerly called the assault carbine. It will apparently have a new title but that hasn't been mentioned as of yet. Anyway it has been described to have the characteristics of and old weapon we know that was good at "mangling" an opponent's shields. So, now instead of being a "depleater", it will be a "finisher".
To me this sounds very much like it could be a remake of the SMG. Thoughts anyone?
I'd personally love if it came back, especially if it was more useful like it was in halo 2.