Microsoft launched the first Windows 10 Preview for phones on February 12, but the company surely disappointed millions of users out there when it decided to make it available on a handful of devices, most of them low-end models.

But that's going to change this month, sources say, as the company is working to expand the Windows 10 preview program to include more phones but also to provide access to a number of new features.

First and foremost, the confirmed things.

On PCs, the next Windows 10 build will come with Spartan browser, thus providing users with their very first chance to try out the application that's soon going to replace Internet Explorer once and for all. To keep phone users updated as well, the company is now planning to ship a testing version of Office Touch in the next build.

Microsoft's Julia White has already confirmed at the MWC 2015 in Barcelona that Office Touch is set to arrive on phones sometime this month, but no other release specifics have been provided for now.

Flagship support also planned

At the same time, it appears that Microsoft is hard at work to bring the new Windows 10 for phones preview on high-end devices running Windows Phone, including Lumia 930 and 1520.

We've received hints that the company is planning to specifically add support for these phones in the upcoming build, not only because it needs to get feedback from all its users but also to fight criticism after the first wave of releases in February.

Right now, Microsoft is already internally testing Windows 10 on a wider range of phones, but not all of them will be supported in the next build. A release for flagships is, however, a priority for the company right now, so expect high-ends to get it very soon.

As for the official release of this new build, no date is known at this point, but expect it to launch by the end of the month, most likely a week or two after the PC version.