A new report on March 26 from Tom Warren at The Verge adds a bit more fuel to the GDR2 fire. According to Warren's sources, Microsoft may reintroduce FM radio support to Windows Phone as part of the GDR2 release. (Windows Phone 7 and the Zune HD both include FM radio support.) Warren also is reporting Nokia is building its own firmware improvements into GDR2, including a screen-activation gesture allowing Lumia 920 and 820 users to double-tap the screen to wake the device from standby.
The Portico (a k a 8.0.10211.204) update was considered GDR1, my sources have said. Microsoft began rolling out Portico in late 2012; I only got it a couple weeks ago it on my HTC 8X on Verizon. Portico included some minor messaging, wi-fi and Internet Explorer updates.
I have heard there will be a third Windows Phone 8 GDRs before Windows Phone Blue, but so far have no information as to what might be in it. I've also heard Windows Phone Blue could be either a late 2013 or early 2014 deliverable.
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.