Leaks about an alleged new HTC Windows Phone in the works have a number of WP watchers wondering what a "GDR" is and how it relates to Microsoft's plans for its mobile platform.

The Windows Phone division has gone larely quiet, as of late. This seems to be a strategy, given PC Mag's report about Microsoft's back-room goings-on from Mobile World Congress in Barcelona this week. "Shut up and ship" is the Windows Phone team's new rallying cry, PC Mag says, with commitments from officials to stop talking about new platform updates "months and months" before they are available.

Given that caveat, it's no surprise that we haven't heard anything about what's next for the Windows Phone OS from the team. Company officials aren't fielding questions about "GDR2" which is listed by UnwiredView.com as the operating system powering the alleged HTC Windows Phone "Tiara," due out this summer.

Here's what one of my sources -- who has been in-the-know about Microsoft's OS plans -- told me.

GDR stands for "General Distribution Release." It means a product update distributed commercially. It's a naming convention that various teams at Microsoft have used for years.

"Portico, " which was the Windows Phone update that Microsoft, handset makers and carriers have been distributing over the past couple of months, is considered the "GDR1" update to the Windows Phone 8 OS, I hear.

GDR2 is the next Windows Phone 8 update. If the leaks about the HTC Tiara are correct, that OS release should be done in the next couple of months so that it can be preloaded on new Windows Phones coming this spring/summer.

I hear from my contact there's also a GDR3 on the roadmap. I have no information on what's in this or when it's slated to arrive.

After that, it's Windows Phone Blue . Windows Phone Blue is the Windows Phone OS update designed to bring the Windows 8, Windows RT and Windows Phone 8 app models and developer platforms more into sync. Supposedly the Windows Blue update includes new programming interfaces, kernel updates and some user interface enhancements (though nothing too major on the UI front, I've heard).

And about that "Apollo Plus" thing ? From what I'm hearing recently, Apollo Plus isn't a codename for some Windows Phone OS update to Apollo (a k a the Windows Phone 8 OS). It was just a name the Softies used at one point to refer generally to updates to the Windows Phone 8 OS. I have no further information as to when/whether VPN connectivity is still on the roadmap , maybe as part of a GDR update, Windows Phone Blue or something beyond that.

The best news in all this, if you're an existing Windows Phone 8 user: All these GDRs and the Blue update itself should work just fine on your phone, according to Windows Phone Senior Marketing Manager Greg Sullivan. PCMag says Sullivan is claiming that Windows Phone 8 users should have nothing to fear from the coming upgrades.

In other Windows Phone news this week, there's an updated version of the official Twitter client for Windows Phone available in the Windows Phone Store. (Still no word on when that promised Twitter client for Windows 8/Windows RT will finally arrive.) And there's a new voice-activated assistant, Maluuba, for Windows Phone in the store, too. It's a Siri for the rest of us, they say....