Work on GMMP 2.0 has been underway for about a month and a half and I am making good progress. GMMP was originally built in the froyo/gingerbread era so there is a lot of custom code i had to write that nowadays is handled by great 3rd party libraries. I've made good progress bringing the code base up to date to the jelly bean / kitkat era, but still have a bunch more to do before I even begin with the UI redesign.
For those curious, yes GMMP 2.0 will follow the Material Design Guidelines. I will do my best to still keep the existing holo skins in some form. Switching development to android studio/gradle from eclipse will make skin maintenance much easier (build variants are awesome).