What is the release schedule for the ubuntu branches?

Solution 1:

The closest thing to "official" that you can get is "when its ready."

Generally speaking, they are released on the same day, however this is not set in stone, because there might be a release blocker that pops in late in the cycle.

For example, Xubuntu 11.10 was released on 13 October 2011, as was Kubuntu and normal Ubuntu.

10.04 Kubuntu, Xubuntu and Ubuntu were also released on the same day (29 April 2010).

As of right now, it appears that official derivatives will be released on the same day as "normal" Ubuntu 12.04.

As per GridCube on the #xubuntu irc channel:

15:44:57 <jrgifford> Hey, quick question: Is the Xubuntu 12.04 release date currently set as the same date that "normal" Ubuntu is? (that is, April 26th) 
15:45:12 <GridCube> jrgifford, yes 
15:45:15 <jrgifford> i can't find a official release schedule wikipage or anything like that. 
15:45:17 <jrgifford> GridCube: thanks 
15:45:19 <Unit193> Should be, maybhe a respin after. 
15:46:42 <GridCube> jrgifford, https://wiki.ubuntu.com/PrecisePangolin/ReleaseSchedule 
<jrgifford> GridCube: so is that release schedule for all official *buntu's? 
15:47:40 <GridCube> jrgifford, for oficial derivatives, yes 
15:47:49 <jrgifford> GridCube: gotcha, thanks! 
15:47:58 <GridCube> like ubuntu/kubuntu/lubuntu/xubuntu

The release schedule is available on the Ubuntu Wiki here.