Here we were, thinking Windows 7 was simply a codename (and a fairly boring one at that—where's Longhorn? Whistler?). Now, on the official Windows Vista Blog, MS has came out and declared "Windows 7" the official name of Vista's successor, dev-only pre-betas of which will be released at the upcoming WinHEC and PDC developer conferences over the next few weeks. The reason why probably makes sense, to someone, somewhere...
The decision to use the name Windows 7 is about simplicity. Over the years, we have taken different approaches to naming Windows. We've used version numbers like Windows 3.11, or dates like Windows 98, or "aspirational" monikers like Windows XP or Windows Vista. And since we do not ship new versions of Windows every year, using a date did not make sense. Likewise, coming up with an all-new "aspirational" name does not do justice to what we are trying to achieve, which is to stay firmly rooted in our aspirations for Windows Vista, while evolving and refining the substantial investments in platform technology in Windows Vista into the next generation of Windows.
In the end, though, names are just names. Remember the outrage over Wii? Now who even gives that a second thought? I've also thought the cat-based naming of OS X was always a little hoaky; I still like the Secret Service-inspired code names better. What would you have called the next Windows? [Windows Developer Blog]