A lot of competitive games that MLG supported then quickly abandoned were never revitalized by the community. It seems that the MLG community at large pretty much only follow whatever MLG is doing. Tons of people wanted Gears 1, Rainbow Six Vegas, and Shadowrun to stay on the circuit, but they never really tried to keep it alive themselves. With Gears 1 and Rainbow Six Vegas, they just waited for the sequel (which disappointed most) and forgot about getting the first game back on the circuit. With Shadowrun, the small community just dissolved and most of the old veterans moved on to something else. The rest just played online community tournaments and never had a legitimate shot to get it back on the circuit because of how niche the game is.
The same thing happened with previous Halo games, people would rather play Halo 3 than Halo Reach, Halo 2 rather than Halo 3, and Halo CE rather than Halo 2. But, they just rolled with whatever MLG did, and never really tried to change anything. Just complain for a few months and deal with it or move on to something else.
I don't think MLG Halo fans will let competitive Halo go away, like the Gears 1, Shadowrun and Rainbow Six Vegas communities let their games die, but it will take a lot of effort to get these MLG sheep to finally try to do something on their own.