Can it really be time to update Xen again?
Yes it can, because the Xen Project has announced a new maintenance release, version 4.4.4, that ticks off a list of 70 fixes and improvements, plus another five qemu quirks.
Xen's had a rough time of it lately, with several severe bugs demanding attention. A few security-related fixes make the list of changes in version 4.4.4, but there are also lots of useful bug fixes like issue c3049fa: “don't reuse ports that are still 'busy'.”
Importantly, this is the last coordinated release of the 4.4 stable series. That means there's no more development to be done: it's all maintenance from here on in. Which doesn't mean it's time to walk away from Xen 4.4, just that you can't expect much by way of innovation from here on in.
Xen's current version is 4.6, with both it and its 4.5 predecessor under active development. Xen 4.7 is due on June 3rd, 2016. The project will thereafter shoot for six-monthly releases, as it's felt that it is better to set realistic goals for more frequent releases rather than shooting for bigger releases with higher likelihood of delays. ®