A looong time ago, i.e at the opening of Disneyland Paris, back in 1992, when one bought a map of the park, you could see a Little Mermaid attraction in the Fantasyland area with these words "future attraction". Well, it was such a "future" attraction that it never opened, and probably will never will, at least in DLP.
But all is not lost as the idea to bring a Little Mermaid attraction at Disneyland, Anaheim is seriously in talks.
One month ago, at the opening of the Finding Nemo's submarine voyage at Disneyland, Ed Grier in an interview to a web site cited "...his personal favorite as The Little Mermaid... "The Little Mermaid continues to be a Disney classic," he said during a roundtable talk at Main Street's Opera House, noting that the animated version of the Hans Christian Andersen story has been adapted for Broadway. "Imagineer Tony Baxter has done great work on a Little Mermaid-based attraction. Have we officially drawn plans up? No, we haven't. But I think we can one day."
Mind you, this doesn't mean that a definitive decision has been done to bring the Little Mermaid attraction for sure at Disneyland. So don't get too excited right now.
But the good news is that legendary imagineer Tony Baxter was recently named as the Imagineer in charge of Disneyland - to supervise Disneyland's development. And, as the Little Mermaid project was created by Tony Baxter AND that it is a great dark ride project, my feeling is that it's time again to cross our fingers and hope that Ed Grier will make the right choice between eventual different concept around the same theme.
You can read more about it and see renderings and a video of a virtual creation of the ride on the disney and more site.