I'd play it, but I wouldn't be happy about it. Seems like a dumb idea at this point to change the genre. Third person shooters play a LOT differently, and while fun for campaigns, aren't as good for multiplayer. And that's 90% of the fun of halo.
I played Halo Wars and that was a RTS. It was better than ODST so I wouldn't really be bothered. I play third person shooters a lot anyway and they are great. For example, the Red Faction series, Gears of War series, Mass effect series( Mass Effect 2 best game ever)