(Pocket-lint) - Microsoft CEO Steve Ballmer says there could potentially be 500 million users of the software giant's forthcoming operating system, Windows 8, by the end of 2013 as that's the number of Windows 7 devices that could be upgraded.

He has also revealed that the company sees the new software as a "rebirth of MS Windows", not just an upgrade.

Speaking at the Seoul Digital Forum in South Korea, Ballmer called Windows 8, the "deepest, broadest and most impactful" Windows experience yet, and and said he believed its SkyDrive cloud computing integration would keep it as one of very few operating systems adopted by PC users.

Discounting Google Chrome, Ballmer predicts Windows will be among a small handful of cloud-connected operating systems that developers will want to support. "The number of core [cloud] platforms, around which software developers will do their innovation, is not ever-broadening," he said.

"It's really a quite smaller and focused number - Windows, various forms of Linux, the Apple ecosystem.

"There will be just a few ecosystems that really can get the critical mass."

Windows 8 is expected to be released in Autumn this year, with a preview build being made available in June.

At the forum, Ballmer also revealed that Skype powered by Windows 8 will be launched soon, now that the video calling service is owned by Microsoft.

Do you think Windows 8 will be a success? Let us know in the comments below...

Writing by Rik Henderson.