Here's an interesting addition coming to a future version of Android. Apps that don't properly scale up to Honeycomb tablets' greater resolution and larger screen sizes will be able to be zoomed in on to properly fill the screen. This is different than stretching the app to fill the screen, which is what happens now if the app doesn't properly target Android 3.x.
Instead, if you tell the app to "Zoom to fill screen," the app will be emulated at approximately HVGA resolution (that's 320x480) and then scaled up. The down side is that things will look pretty pixelated, but usability shouldn't be affected.
You won't see this on every app you run on Honeycomb -- many apps were designed to scale up on their own just fine, thank you very much, and so developers can remove the stretch/zoom option if they so choose.
And since we know you'll ask, Google's not yet saying what the next version of Honeycomb will be, though we've seen evidence that it could be Android 3.2.