Well the market is wide open for a modern sub sim, with the graphic's of SH-4. Also no sim at the moment (that I know of) includes the latest AIP subs, so with that in mind and knowing UBI it more then likely won't happen
. They could still make money out of SH 4 though by including add-on's, say to include US PT-boat's or playable RN - IJN subs.