So when is the expected date for GFX and the m-c trees to merge ?
Around March 18th, as long as there are no unexpected problems. This is our goal date, not a promise :-)
[...] a lot of the OMT* is being done on priority for FFOS and Android, and later trickling to desktops. Has the traditional desktpos (win, lin and mac) market become second tier platform for mozilla ?
No, certainly not, although we have a lot of work to do on mobile, so that is a focus for many engineers right now. OMT* is developed for mobile because it is needed most there. Without OMTC, Firefox for Android is really unusably bad. Without OMTA FirefoxOS is really slow and jittery in some key places. Desktop Firefox works pretty well without them (although it will work better with).
Why is that OMT* work lags on windows, compared to OSX and Linux ? AFAIK, windows makes 90% of mozilla users. So shouldnt windows desktop get more priority ?
As I said above, the focus of the OMT* work has been for mobile and that means OpenGL. We don't support OpenGL on Windows, so we don't have OMT* there. We only have it on Mac and Linux to make mobile development easier - it is not yet a supported configuration on either platform (although it will be in the future). Implementing OMT* on a different graphics backend has been very daunting. One goal of the layers refactoring is to make that easier. Our current focus for OMTC is Windows, in particular for the Metro browser. Unless there are unforeseen hurdles, Windows will be the next platform to get OMTC. (OMTA has a few other issues before it can be used anywhere other than FirefoxOS (including on Android), not least of which is testing).
And yes, Windows is a higher priority for Mozilla (in general) than Linux and Mac, although user share is not the sole determinant of priority (Linux gets a lot of love (relative to its user share) because it is more closely aligned to our mission and a lot of developers use it, for example).