MGS 5 is coming to Xbox also. Not to mention Brawl has references to Son of The Patriots, which means that his not appearing on Nintendo consoles problem is minute.
I really don't see him getting cut. He WAS the first 3rd party character in Smash Bros ever. If Sonic didn't get in, the only 3rd party would've been Snake anyway. Really, if we're getting mainstay 3rd parties, Snake needs to stay.
Plus, whenever I play as him with my friends and I get a Mega Mushroom, I like to shout, "HUGE BOSS!" and then kick them with Snake's meaty legs