It'd either have to be a heavy, thick tablet that generated a lot of heat, something that keeps compact tablets (like the iPad or the Xoom) from functioning, with the heat shutting down the processor (or destroying it if the processor doesn't shut down).
Alternately if they made very significant battery advances (quite a bit beyond anything they're realistically looking at for the next couple of years), it'd be a not-so-heavy, not-so-thick tablet that generated a lot of heat and would shut down.
They could build a non-compact tablet where there's room for fans and airflow that was laptop-thick and laptop-heavy that ran full-blown windows and didn't use a low-power processor and... wait, that's what they've done for the last 8 years, and almost nobody bought them.
I'm pretty sure they'll have to go low-power. That's why Microsoft recently announced that the next version of Windows will also run on ARM processors: Intel doesn't have a sufficiently powerful processor that's also cool enough and easy on the battery. They're working on such processors but, even with those it's still a low-power world.