The Linux Kernel version 4.0 is available in the official Fedora repositories for users running the alpha release of Fedora 22.
2 Weeks ago Fedora 22 Alpha was released (read more about it here) and last Sunday Linus Torvalds released Linux Kernel 4.0, after the last RC7 release. It is labeled as a stable release & features a lot of improvements. Read more about the Linux Kernel 4.0 release here.
To get the updated version of the kernel on your Fedora 22 machine, either update the system via the Software application (in Fedora Workstation), or using dnf update on the command line.