While there nothing really stopping you, I'd suggest you hold off on upgrading the kernel until you find you actually have a need for it.
While the later kernels do have a whole slew of cool features, making the current release of SME play with them nicely is not an easy task. (Hence why most of us leave it up to those happy chappies over at Mitel).
If you find a killer application that requires a later kernel and you can't wait for the next version of SME, then go for it... ,otherwise, save yourself a whole lotta pain and be confident that the currently supplied kernel does a pretty spiffy job at most things already.
Regards,
Luke