I have it from a good source that SDC has actually been toying with this idea for a long time, testing out various types for water cannons in the boat houses among other research. This ride is practically confirmed for the park. This source was also sure that this would indeed go in the Landing and that it would be built this year, not the next.
Hmmm...
Well, in any case, I'm really looking forward to this. I think the Splash Battle is only one part of this whole offering, which I expect to include a re-make of the buildings in the area hopefully with some new shops and thematic elements. Like Swoosh said, this is a very welcome re-establishment of a uber-favorited section of the park. It really is a win in all directions, though I'll still keep my nose up if they use plastic in the thematics. I really think they'll actually do a better job at theming it than some of us will assume at this point however - the concept artwork and description seem to show off a real attention to detail like we haven't truly seen since Wildfire. River Battle at DW was just a ride, but this I can see being a true experience all around. I'm looking forward to seeing Huck Finn back in the park.