In one word: history.
They won't be enjoying the same market position they had with the PS2, and any delusions that SCE can sell their new console for whatever price they want should have long left the building.
Assuming SCE doesn't try to reinvent the wheel again and instead build off the current platform (updated CBE, current GPU, reasonable amount of both system RAM and VRAM), there's no reason why they shouldn't be able to keep both R&D and more importantly, production costs to a minimum.
As the general consensus seems to agree, any price over $399 is simply asking for a repeat of the initial reception of the PS3. Initial game catalog really can't change that either as they will still be first year efforts on a new platform.
More focus should be placed on online services and content distribution, which is essentially a given. Depending on how the tail end of the current generation swings, more emphasis may be placed on alternate control schemes as well rather than just the tried and true gamepad.
