Well yes its the same engine but 343i said its been upgraded a bunch and look at the halo 1 remake campaign, halo reach campaign was super laggy when played with others on xbl, but halo 1 has even better graphics than reach and doesn't even lag at all most of the time, even on big *** maps like silent car. and such. so i think the engines capabilities will be much stronger and be able to hold much more than what we've seen.