Xen _hypervisor_ will not make it into the kernel, because there's no point in that. It's not part of Xen design.
Linux support for Xen hypervisor is already in Linux kernel.
Whatever. From the last few months of testing with Xen, I really could care less about running anything on it.
I like the comfy feeling I get when I see that I have one less place to hit for troubleshooting/compromising with the kvm solution.