Much hunch is this is part of something that was proposed long ago when the suits decided there needed to be something new at the park to drive attendance and before the (correct) decision to totally refurbish the place, bringing this most beautiful of all Magic Kingdoms up to Disney show standards. Perhaps is was even proposed before the bones of the California Adventure attraction became the backbone of the Grizzly Gulch's Runaway Mine Cars of Hong Kong Disneyland. Recycling in the parks is such a common occurrence, but so far, if you've noticed, nothing makes it over to the other parks if it came from Tokyo Disney Sea.
Certainly this addition would more appropriate to the theme than Splash Mountain, which is full of cartoon characters and once also proposed for this park. I'd hate to see the further cartooning of the lands there.
However, a rapids ride is full of water, much more so than Splash, and Paris has very cold winters. I've been there in late October and in January, and it is already cold and sometimes harsh even in the Fall. So, we shall see how this plays out. However, I bet the Imagineers are on to something new for the park once all the refurbishments are complete.
(Concept art copyright The Walt Disney Company.)