There is no version of mobile Firefox whether old or upcoming for any Blackberry OS's and not planned for in future. It also does not help that support for QNX has long been removed from the Mozilla source tree. In past some were able to side load some Android versions of Firefox onto BB10 but it is not without issues. BlackBerry of course never ported BB10 for PlayBook as was promised. I have a 32 and 64GB Playbooks myself.