Rhine River rafts will never come as a log flume kind of ride, mainly because Maelstrom, two similar rides in the same area, yes theming and detailing maybe different, but in essence the experience to very close to each other.
Not that the ideas here arn't very good, just i cant see it happening any more with the current trends in Epcot.
A slow moving boat ride thru scenes is OK to be duplicated (i.e. pirates and small world), but again i hope they dont. Personally I hope that if something new comes to WS, I hope its something unique, not just something added for the sake of adding something.
After all you could do a river tour for the UK pavilion, a trip along London's Thames. Easy to do, some great things to see, but again not to exciting or very unique to WS. Same could also be said about Paris....!
Its a tough one, they could just go down the Fantasyland route, and make loads of slow-boat ride and dark rides, but there's nothing there that would bring in the big numbers.
I appreciate that it increases interest and capacity, but i think there are better ways.
I like the idea of the japanese Shinkansen that was in another thread the other day. It's unique, but also gives you a unique feel and look at Japanese culture.
Still I guess after almost 20 years without anything new, maybe something is better than nothing..............!