Microsoft is expected to launch its new Windows Phone 8.1 operating system in the next couple of days. However, the availability of the mobile platform will depend on region and carrier, so the update will surely not be available for everyone at the same time.

Still, Windows Phone fans have already been able to get their hands on Nokia's Lumia 630 and 635, the first smartphones launched with Windows Phone 8.1 out of the box.

Aside from the two handsets mentioned earlier, Microsoft is now rolling out the Lumia 930, its best Windows Phone 8.1 soon to be available on the market.

But these aren't the only Windows Phone 8.1 handsets to make their debut on the market this year, as Microsoft is expected to launch a few more smartphones by the end of the year.

The codenames of some of the upcoming Nokia Lumia smartphones to be released by Microsoft in the coming months have just been leaked online. According to @evleaks, Microsoft is currently working to bring the Nokia Vela, Athena and Libra to the market.

Unfortunately, aside from their internal names, nothing else is known about these smartphone. The good news is that we now know that Microsoft's upcoming lineup of handsets contains at least three devices.