I recently visited Screamscape.com, a site that meets mixed reviews here on this site, but I personally have found to be at least moderately reliable, and they mention a persistant rumor of adding Tokyo DisneySea's Mermaid Lagoon in a revised form to the Magic Kingdom, in the place of 20,000 Leagues.
The editor of the site claims to have received many messages claiming this rumor, which states that the announcement for the construction would come with the release of the Little Mermaid on DVD next week.
I would like to hear your thoughts, but first I thought I'd share some of my own...
The Magic Kingdom is in need of a descently themed children's play area/ general themed area, and the Mermaid Lagoon would fit in very well with this proposed location. Ariel's Grotto already occupies a location very close, which would provide an excellent lead in to a new attraction area.
According to eyewitnesses, Imagineers were conducting balloon tests over the site recently, I personally witnessed what appeared to be a preliminary land-site survey in that location when I was on my CP last year.
The Florida climate would merit the construction of a wholly indoor land, giving the visitors to the park a chance to get indoors without having to go on a specific attraction or going into a crowded merchandise location.
The Magic Kingdom has been receiving very few "plusses" in the last few years, getting smaller, cheaper additions instead. With the amounts of money thrown at the other parks, it is reasonable to assume that a similar amount was delegated to the Magic Kingdom, and that those funds may be in a state of savings to prepare for a new construction.
Currently the Magic Kingdom has both Mickey's Toontown Fair and Pooh's Playful Spot for children, which in managerial terms merits no further capital expending construction.
There have been no previous serious mention of this throughout the Walt Disney World community, which would suggest that this is truly just a wild rumor.
The construction of a full scale land on the scale of Mermaid Lagoon would be a serious investment for the company. With impending celebrations for Epcot's 25th, as well as Midway Mania and other such additions, it is unreasonable to assume that the Magic Kingdom would recieve the amount of funds needed for this.
The Little Mermaid is a marketable franchise, but without theatrical release, the reception to the introduction of the DVD will be limited. I would anticipate an "observation" period, where Disney will watch the reaction to the release.
Many such rumors like this have existed before, ranging from the renovation of Space Mountain to the addition of Raging Spirits, and so far, all have come to not.
Those are just a few of my differing perspectives on this rumor. I personally feel that it is just a flight of fancy, but I would see the addition of a land like this to be very positive for the park. A mermaid-themed addition would add a sense of pure fantasy to the park which has had a very strong identity crisis as of late. So in the end, while it would be a good addition, I wouldn't get my hopes up.