You can use the Xfce 4.12 PPA [1] which is managed by the Xubuntu Developers. However, not all packages are updated to the latest version yet.
I would suggest that you simply download Xubuntu 15.10 (current development release) and boot into the live session to test the new xfwm4 version.
[1] https://launchpad.net/~xubuntu-dev/+archive/ubuntu/xfce-4.12
You can use the Xfce 4.12 PPA [1] which is managed by the Xubuntu Developers.
However, not all packages are updated to the latest version yet.
I would suggest that you simply download Xubuntu 15.10 (current development release) and boot into the live session to test the new xfwm4 version.
[1] https:/ /launchpad. net/~xubuntu- dev/+archive/ ubuntu/ xfce-4. 12