Roadmaps and release schedules are good, but the best time to release software is of course "When it's ready" (Something the commercial software world needs
I don't particularly care about GTK+ 3 support (I don't have it, as I don't need it for anything) but if that's something they are striving for with the release, they are doing the right thing if they need to go back to the drawing boards on some parts of the project.
XFCE has mostly been good quality, in the 10+ years that I've been using it and I wouldn't want that to change. (Starting back when it was based on GTK+ 1.2.x and made "boingy" sounds when you clicked on stuff. It got old fast, but none the less I couldn't bring myself to disable it because it was so amusing at the start. I wasn't sorry when it went away, though.)
Any bugs that I encountered (e.g. configuration functions that didn't quite work as expected, like being prevented from dragging things where you want them on the panel) I was always able to work around somehow.
I don't always have to have the latest release of XFCE though... I tend to build one and stick with it for the life of the Linux install which could be years. Once I have it all configured my way (a specific way that I like... more like old versions) it doesn't get broken. It keeps working without a recompile even when you upgrade the libraries it's linked against. (within reason)
I had to check (couldn't remember, as this system is a few years old now) but I'm still using version 4.6.1 here.
I have a much newer version on my laptop, but I tend to use it the same way so I don't notice any difference. While I'm on that, I was actually impressed that the config mostly migrated from an older distro I had. (I tarred up my home directory and selectively copied back configs) It warned me that it had to convert the panel, but it didn't miss a beat. I just had to put the programs in place that my launchers were configured for and change a few icon paths etc. Why this is significant to me is, XFCE wasn't so good at that in the past and I always configured it from scratch with a newer version.