I do admit I was involved in base sieges and defenses more often than other scenarios. However, I also recall more than a few bridge fights, desperate counter-attacks, and never-ending streams of tanks from a final base that simply refused to give up. Now with PS2 adding in resources to fight for and not just bases, I think there will be plenty of fights involving massed vehicles.
I enjoy a good infantry only fight now and again. Or a MAX push. Or a gen drop behind enemy lines. Planetside 1 gave us a plethora of ways in which to kill each other, and Planetside 2 is going to give us even more! I'm sure they'll come up with inventive ways to make us want to get out of tanks and planes and into some trenches.