Since a few hours it’s possible to install Shiretoko Alpha 1+ from the openSUSE Buildservice.
Warning:
These packages are just provided for testing and are nothing for the faint heart!
They are designed to be installed in parallel to other Firefox installations but it will use the same profile as your other versions if you don’t take care.
You should create an alternative profile by executing firefox31 -no-remote -p and remember using the correct one later using the parameter -P. (And create a backup of ~/.mozilla/firefox!).
I’m planning to do occasional updates but at least will try to follow the upstream milestones.

One-click install