That’s right, they are still tracking the development of Linux kernel 4.10 for Ubuntu 17.04, and it looks like the recently released RC6 build has hit the unstable repositories, and you can take it for a test drive right now if you manually install the binary packages from the link posted by the Ubuntu developers below. Meanwhile, they’ve rebased the kernel packages of Ubuntu 17.04 (Zesty Zapus) on the upstream Linux 4.9.6 kernel release, tagging the new kernel version as 4.9.0-16.17, which currently lies in the proposed (pre-release updates) channel if you want to take it for an early test drive as well.