This article in the NYT offers a little light on Sony's thoughts about the next PSP console. Perhaps the key takeaway is the line
“Depending on the game, there are ones where you can play perfectly well with a touch panel,” Mr. Hirai said. “But you can definitely play immersive games better with physical buttons and pads. I think there could be games where you’re able to use both in combination.”
So, once again Sony aims to be jack of all trades, lets just hope it won't end up a master of none, as the media features of the first PSP have proven - I mean it has only just got its first proper music store in Europe - makes you wonder where all the vision was at the launch?