The short answer is yes, if it meets the criteria it can be patented. You'll notice every time Full Tilt mentions rush poker in an e-mail or press release or whatever they'll proudly tell you they have patents pending on it.
Once a game variation is patented anyone else who wants to offer it has to pay the patent holder a licensing fee.
This is a big money business in live casinos
BTW. The guy who patented the Perfect Pairs side game on blackjack
tables a few years ago is filthy rich now because casinos around the world want that game on their tables and they all have to pay him a fee for the privilege. I'm sure this is what Full Tilt has in mind for rush poker too.