Engadget is reporting that, according to a "particularly reliable tipster", Sony may not be completely giving up on UMD cartridges for the PSP. Their unnamed source claims that Sony is planning a PSP-4000, which will include the UMD drive, and will be sold alongside the PSP Go. As you know, since the Go became official, it has been assumed that the UMD would go the way of Betamax and HD-DVD. However Engadget is claiming that this rumor has an air of believability to it, since the source it came from also accurately predicted the PS3 Slim all the way back in June.

I generally avoid these kinds of stories, only because there seems to be so much room for conjecture or straight-up fictional information. There's been no word from Sony as to the veracity of these claims, but that's nothing to be surprised about. Although Sony is probably the worst at keeping industry secrets, it's also a company that will refuse to substantiate rumors until it's time to make an official announcement. I guess we'll just have to wait and see.