Sad but true.
The deal with bringing back Halo 2 multi is the ultra diehards will want it back with the glitches included. This isn't really viable in a modern online FPS so 343 will have to fix the glitches. Then you'll just be seeing a lot of "it's bastardized Halo 2".
Then they'd have to update every single multiplayer map to modern standards. Certain Affinity has to make CoD maps too so they won't have the time to remake 12+ Bungie maps again for the third time.
Then it'd split the userbase anyway. As we saw with the Reach Anniversary disc.
Better off just making H2A then remaking a couple of the maps for whatever the current Halo is