About the only thing that could really stop them from doing an official HALO RPG would be the cost of buying the license. I know that other properties have gone unclaimed as RPGs for that reason.

I have actually thought about running HALO using Terra Primate and AFMBE. With Beyond Human coming out later this year, I may yet do it. Problem is, I also want to run Jurassic Park and a couple of other settings too. Decisions, decisions.