Jailbreaking is about exploiting BOTH the hardware and the OS.
I would stake my reputation (FWIW!) on the fact that the limera1n exploit will be well and truly dealt with by Apple, therefore the new A5 devices are not pwnd for life like the A4 based ones... However, iPad2, like every other iDevice, will for sure be jailbroken at some point in time, but a new exploit will need to be found.
There is of course an outside chance that unreleased exploits shuch as shatter may still be active on the new hardware which could speed the process up :D
Lets hope so!