Wasn't part of the motivation to release UBM for SH4 the fact most of the resources were already at hand? Considering this is "all new code", I'd imagine we won't see a return of fleetboats untill SH6, or perhaps a very extensive expansion.
I wouldn't mind paying (close to) full price for an expansion for SH5 that adds content on the scale of the original game... but then they might as well release it as SH6.
