Ugh, i hope not. I don't mind a Battlefield-style Halo spin-off with larger player count but normal Halo should stick to 16 max (or thereabouts anyway). Larger player counts become quickly impractical, it affects sandbox balancing, and too large maps don't necessarily work for smaller modes whereas certain BTB-size maps do work (as they are, naturally larger maps can be sectioned for smaller modes but that's extra work).
This said, i suspect it is something else than large player counts. AI, physics, destruction are some possibilities, or there could be persistent universe aspects akin to Destiny (not saying i want this), or whatever else.