I believe they wanted to do something Halo 4 related during Dallas.
And it'll very likely get picked up, it was confirmed there'll be classic playlists/playlists that don't utilize the use of Loadouts/abilities, which I guess are the same thing lol..
So there's a lot there for MLG to work with, especially if the customization in Custom Games is very vast, which I think will be, so it'll provide a fair playing ground.
Maybe their gametypes will have loadouts where people can choose DMR, Carbine, or Battle Rifle, and no Abilities/Mods. We'll just have to wait and see how vast the customization is when Halo 4 releases.