iv seen many theory's and they are all believable like idea you play as odst and sure maybe not and the idea its based on the books but lets face it there is no solid proof for any ones theory i could say youl play as a grunt (highly unlikely ) but still possible we know nothing . we have a trailer that proves nothing but that Spartans that will appearin the game , a banner that could be a mix of allies and enemy's and the odst vidoc that states buck was on reach .there's also no proof it even takes place on reach . Who knows maybe time travel will be in the game. we know nothing so before you go and flames some ones theory just remember for all we know any thing is possible .