hello, i know of no ongoing development or efforts by mozilla of porting firefox to the windows phone platform. originally there have been technical and legal hurdles in the app store which discouraged mozilla from starting any developments in this direction. i don't know about the current situation, but since mozilla is now focusing its energies on creating firefox os as open source web-based platform, i doubt that you will see firefox on your windows phone device in the foreseeable future...

Hopefully Edge is all Microsoft is saying it will be.