It's being rumoured that Sony will be announcing a PSP-4000 in 2010. Edge is reporting that the Tokyo Game Show this year was full of whispers that the PSP Go hasn't been selling at all well, and that Sony has decided to reverse the decisions made and return to the UMD format.

The PSP Go launched with a rather large price tag, and a limited catalogue of games, as well as a poor upgrade experience. Sales rocketed 300% in the first few days that the PSP Go was on sale, but appear to have fallen off just as quickly. As a result, is Sony stepping back from its digital-only strategy?

We won't know for sure until the company makes an announcement one way or another, and Sony Computer Entertainment UK refused to comment on this story. Until then, we'd be interesting in hearing your thoughts - do you have a PSP Go? Do you miss the UMD? Or have you refused to get one thanks to your catalogue of UMD games and movies?