For those wanting to try out the latest development version packages for Xfce 4.13 (which will become 4.14 at the stable release) in Fedora, user 'nonamedotc' has set up a COPR repo to try out.
The COPR repo provides packages for Rawhide, Fedora 25 and Fedora 26 and as one can imagine, anything that goes wrong and/or makes your computer catch on fire is completely at your own risk. It is after all, for testing purposes.
Enabling the COPR repo is easy with the dnf command:
dnf copr enable nonamedotc/xfce-414
nonamedotc says to report any bugs to the "Pagure" git repo, which allows submitting issues in a similar way to GitHub. For more on that, see nonamedotc's blog post.
Being Xfce, I don't personally imagine there will be too much in the way of instability or huge bugs, but still, take care and enjoy.