Here's the (somewhat brief) official statement:
Nokia Belle is the latest Symbian software release with all-new user interface, improved user experience, and dozens of improved and new features. We have already shipped Nokia 603, 700 and 701 with Belle software this year, and have received great feedback on the new user experience.
We will make Nokia Belle available to consumers globally by rolling out the Belle software for the existing Nokia range of smartphones such as N8, E7, X7, C6-01, C7, Oro, E6, and Nokia 500 in early 2012. With that, millions of consumers around the world will get a totally fresh experience on their Symbian smartphone.
Although it's tempting to use the word 'delay', I can't find an official statement promising a date in 2011 for Belle updates for existing devices. The extra wait time is frustrating, of course, to say the least.
I suspect that Belle is already being loaded onto N8s and C7s coming off the production lines (can anyone confirm this?) and that the 'update' for existing devices is taking longer because of the compexity of ensuring that a major OS update installs cleanly on existing installations without affecting user data and set up. If it was deemed acceptable to have the OS update wipe every phone and user data synced and apps reinstalled, we'd have had Belle already. Such draconian behaviour would cause an outcry from less technical users, of course.
As to what 'early 2012' means, we did note that some Nokia Facebook pages listed Belle as coming in 'February 2012', but as ever, different devices and regions will see slightly different roll-out dates.
And as a final thought, given the prevailing pessimism in the Symbian world after the February 11th declaration of a 'franchising' for the OS we should perhaps simply be happy that the Belle updates are still coming at all? News of further updates beyond Belle is currently entirely unofficial. Watch AAS for official news, as usual.