You know, you can all bitch and whine about this, or you can stop, step back, and think about this logically.
WWE want Batista vs Cena to main event WM. Well isn't it going to be better as the decider, with them at one win each? It's better than a simple rematch from SummerSlam, it's those two finally deciding who truly is the better man, with the World Heavyweight Championship on the line. A pretty smart way to book things, IMO.
Before you say, "O BUT CENA SHULD HAVE ENRNT DIS DEN GOT A MATCH~!" what better event to have it at the Survivor Series? WWE didn't plan this injury, but their still going through with what looks like their original plans, and I like them.