Comment 5 for bug 1546978

It does not necessarily need to as the Trusty version of Xen has everything needed to run in libxl mode. We even have attempted to provide tools to convert the old configurations over from handled by xend into handled by libvirt. There is really no "excuse" to run the old toolstack.
That said it could be a bonus to have a Xen version matching the release of the libvirt used. And I think James has done some backport for the Xen version for Xenial (but not sure which cloud-archive silo for).