It's possible, but a ways off I reckon.
If the game is successful (and it should be, but judging by the chatter at Subsim of all places, it is not so far) then I think we would first see an expansion of the German side. Type IX and maybe Type XXI?
After that a Pacific expansion with US and/or Japanese boats seems natural, if it can be profitable.
There are already Japanese boats in the game, so we are part of the way there
