These threads are always so boring. It always end up with "Sony should pursue the exact same strategy they did for the first one". The problem is, even if we do consider the PSP to be a mild success, the fact of the matter is the same strategy just isn't going to work for them again.
The reason the PSP achieved the success it did was because it managed to capture a good proportion of the niche Japanese game market but the reason it got that market had more to do with the other systems' shortcomings then it's own merits. The PS360 were too expensive to develop for, the PC has no Japanese market penetration, the Wii failed to capture the target audience, the PS2 was reaching the end of it's life and the DS was just too graphically limited to keep the whole market to itself (some of those games just couldn't have been done on it).
However, the same lightning is not going to strike again. The 3DS is a far less limited system by today's standards then the DS was by 2004's standards. The 3DS should be perfectly capable of realising most modern game ideas the same way that PSP1 is still able to. Even if the PSP2 houses more advance components then the 3DS, it will still not be powerful enough to accommodate any ideas that couldn't be done on the 3DS with slightly worse graphics. And when you take into consideration Nintendo's aggressive strategy to grab the current PSP market and the ever growing threat of smartphone gaming, it's easy to see that Sony is going to have to be a lot more creative this time around if they want the PSP2 to succeed.
That's why the perfect PSP2 should not just be a handheld powerhouse or just rip on Nintendo's ideas. The perfect PSP2 should be someone with it's own personality. Something with a gimmick capable of carving it's own healthy niche. What that gimmick would have to be, I have no idea but I'm sure hoping Sony's Engineers can figure it out. It'd be a shame to see Sony loose it's place in the handheld market, things are a lot more interesting with them in it.