Some questions are being asked about the PSP2's massive power in its quad-core processor and a quad-core graphics chip. The answer is quite a simple one. Sony's PSP had a five to six year lifespan and Sony needs the PSP2 to have the same longevity to make a decent return.
While mobile phones, tablets and rival devices are only just entering dual-core territory, Sony has to look to three or four years time when these perennially upgraded phones will start to match the PSP2 for power.
So, while the PSP2 looks like a power demon now, in a few years it will be matched and then overtaken by other devices. If Sony ever decides to upgrade the PSP2, it could run into a host of compatibility issues (such as minuscule timing problems/command function and pipeline changes) that hardcore games developers come up against, something that casual games like Angry Birds never will.
If Sony can leave the hardware unchanged then it makes more money and can guarantee the same experience across the 50-100 million consoles that it wants to sell. Perhaps, Sony does have an upgrade path in mind, but the console tradition is one device with tiny, incremental upgrades - it will be a radical change is Sony starts fighting at the level of feature-phones.