The first Windows Phone 8 smartphones are now on sale, but what about Windows Phone 7.8: the update that brings some of WP8′s new features to older models? Microsoft provided some clarification yesterday.

“New models running Windows Phone 7.8 are beginning to launch in many countries around the world, strengthening the ecosystem by bringing more Windows Phones to more people,” explained Microsoft’s Terry Myerson, before revealing that existing handsets won’t get the update until early next year.

“We know you’re eager to get the Windows Phone 7.8 update, and we want you to know that we’re working closely with our hardware and carrier partners to get it tested, approved, and rolled out to as many devices as possible in early 2013,” wrote Myerson on the Windows Phone blog.

“As we work to quickly get this in the hands of our loyal users, we’re also striving to deliver a high-quality release and ensure a smooth transition for our widely expanded services.”

So, no pre-Christmas update for existing Windows Phone users, which is causing some frustration on messageboards from early adopters. Whether the wait will be a big problem for more mainstream customers is open to debate, though.

The news came as Microsoft boss Steve Ballmer told shareholders that the company is selling four times as many Windows Phones as this time last year, although he gave no firm figures on that.

We can turn to some third parties, mind. Earlier this year, Gartner estimated that 2.8m Microsoft-powered smartphones were sold to end users in the fourth quarter of 2011. If both that and Ballmer’s claim are accurate, it would hint at upwards of 11m Windows Phones sold in Q4 2012.

However, Ballmer’s comments came as Windows Phone 8 smartphones were rolling out with operators around the world, and thus benefitting from any pent-up demand – the sales rate must now continue through December against ferocious competition from iPhone and Android handsets.