So after checking out the forums for a while and other Halo 4 new sources I still have not seen anything about Dual-Wielding. It would be a shame to not see the epic return of the smg.
Dual-wielding added a whole new level to Halo’s extensive combat system that allowed some great customization in-battlefield. Balance issues? Then fix them. Give the Plasma Pistol a longer cooldown after use or have it blow through energy it held charged.
IMO, Dual-Wielding made Halo 2 and Halo 3 amazing cause it gave the gameplay much more depth. Getting rid of it would make Halo’s combat less interesting entirely.