Officially, Microsoft hasn't announced the name of the next Windows release—and the coming September 30 event is about "what's next for Windows and the enterprise."
As WP Central reports, however, that didn't stop Alain Crozier, the President of Microsoft France, from spilling the beans. At a press event yesterday, Crozier apparently stated, "Last year we had Windows 8. In the next few minutes, the next few days, we'll be releasing Windows 9."
Microsoft has since partially recanted that announcement, saying the event is merely about "the future of Windows, which actually at this stage does not have a name as such." Given Croizier's job title, though, I'd be surprised if his slip-up was anything more than ill timing.