The announcement was made at the annual sales meeting by Steven Sinofsky, President of the Windows and Windows Live Division at Microsoft. The news was then posted on the official Microsoft Windows blog. The October 26 date refers both to the upgrade version of Windows 8 for existing computers, as well as the OEM install version for new PCs.
We can probably then assume that the Windows 8-powered Microsoft Surface tablets should be launching right around the same time, since Microsoft probably wants to capitalize on the holiday shopping season as best it can. Are you going to upgrade your PC on day one or are you going to wait for SP1 to iron out any early kinks?