Microsoft's Windows Phone 8 (WP8) mobile platform is less than a year old, but speculations surrounding the next-gen operating system Windows Phone 9 (WP9) are gaining momentum.

Concepts of what the upcoming WP9 or Windows 9 will offer, have previously emerged online, giving one glimpses into what Microsoft could perhaps have in store.

Microsoft released WP8 in Oct. 2012 and market observers are of the opinion that the company will possibly adopt an annual software cycle for its mobile OS platform to keep it fresh and relevant. At least, that's what Apple does for iOS to retain its popularity and appeal.

Rumors have hinted that WP9, also refered to as Windows Phone Blue, could release by end 2013, in time for Christmas. Alternately, speculations are also rife that Microsoft will give WP8 the boot in Sept. 2014. The Redmond-based company may also be looking to merge its mobile OS with the one for tablets and PCs and bundle it all together to give users Windows 9.

Per a DigiTimes report in April, "Microsoft is reportedly developing Windows Blue as an independent project that will help merge Windows (PC) with Windows Phone. Rumors have also spread that Microsoft is developing another operating system, which will serve as the next-generation Windows and will be released in October."

Moreover, in March this year, a Microsoft employee mentioned on his LinkedIn profile that the company was "currently testing Windows 9 OS on Nokia, HTC and Qualcomm device," hinting that the WP9 release could be soon.

Tech analysts are of the opinion that Windows 9 will not be as restrictive as WP8, which basically means that unlike WP7 user who did not get WP8 but were stuck with Windows Phone 7.8, WP8 users will be able to upgrade to the next-gen version of the mobile OS.

It remains to be seen if Microsoft will announce WP9 this year or in 2014. But, for now, all eyes are on the rumored GDR2 update Microsoft is expected to roll out for its WP8-powered smartphones.