initramfs-tools in Debian is on life support. None of the current maintainers has a lot of time for it. Aside from the fsck/mount changes that came far too late into the jessie release cycle, maintenance is mostly reactive. Although the Ubuntu maintainers are doing some work on it, their branch has diverged quite a way and they haven't sent any changes to Debian for a long time.
initramfs-tools depends on udev, which will probably become dependent on D-Bus by the time of stretch release. The system bus would probably have to be set up by systemd running as init. I think that this would require rewriting much of initramfs-tools.
dracut has been adopted by several other distributions and has an active upstream, but it doesn't yet work as well in Debian. In particular, many of the Debian packages that hook into initramfs-tools don't hook into dracut (and it has weaker support for such hooks). It does already support the use of systemd as init in the initramfs.
I believe we have to make a decision soon as to which of these to use by default in stretch, and then begin work on the necessary changes.