My pull-request for matplotlib to add PyQt5 support has been accepted and merged, meaning PyQt5 support will be available in the upcoming v1.4.0 release of matplotlib.
Based off original work by @badders this re-implements the Qt backend structure as Qt5-first, with Qt4 wrappers for compatibility. It's hoped that this will simplify things going forward, keeping the latest API cleanest with minimal code-cruft.
Thanks to the matplotlib team for the support in getting the PR up to scratch.
PyQt/PySide 1:1 Coaching with Martin Fitzpatrick — Save yourself time and frustration. Get one on one help with your Python GUI projects. Working together with you I'll identify issues and suggest fixes, from bugs and usability to architecture and maintainability.