An official Gygabyte UP representative confirmed that the mobility version of the Nvidia GeForce GTX 11xx series should arrive towards the end of the year. This pretty much confirms that the desktop versions are slated to be released this summer, as the mobility solutions usually get released a few months later.
https://www.notebookcheck.net/Nvidia-s-next-gen-mobility-GPUs-confirmed-to-be-landing-in-late-2018.301940.0.html