The technology side is an easy answer, I'd put every future keystroke into Unreal Engine. The money side is way complex. With the investment in several platforms already made (hope you guys can claim R&D tax credits) I would finish the PC version and see how it does. If your commitment to Unreal is solid then there's your future however painful the transition will be (but it will pay off in spades). Man you are dealing with development challenges several magnitudes greater than myself, its very impressive, how do you hold it all together?
Great job, Greg