I think the answer is yes, potentially. In OS2008 the CPU can be run at 400 MHz instead of being capped at the 320 MHz limit in OS2007. It should only run at the higher speed for processor-intensive tasks, and then drop back down in speed (potentially lower than 320 MHz) when it is relatively idle.

So if you are running something that operates the CPU at 400 MHz for long periods, the tablet could feel warmer than it did under OS2007.

Still nothing to worry about unless it gets uncomfortably warm to the touch.