There's been a rumour doing the rounds over the last few days about Aperture that I feel needs dispelling. Apple Insider pointed out that a publisher has a new listing on amazon for a book titled "Apple Aperture X - under NDA: A Workflow Guide for Digital Photographers". If this sounds familiar it's because this isn't the first time an unannounced book has touted the "Aperture X" title. Unfortunately for those getting your hopes up, I'm afraid this doesn't mean that the next version of Aperture is imminent. Publishers commonly use the letter "X" as a placeholder when developing books as the actual version number of the software commonly changes during the writing and development of a book. So, when giving information to retailers such as Amazon they use the "X" version as a placeholder until the book is near release. It's common practice, and given the number of times this has happened and been debunked I'm surprised (well, not really) by the number of sites picking up on this.
That's not to say there won't be an Aperture X at some point, although I doubt it. I suspect that Apple will keep the current numbering convention for a while. Final Cut was a special case, as FCPX was a complete re-write and it was close to version 10 anyway. Aperture is still in the 3.x phase.