The project is called 20,000 Leagues Under the Sea: Captain Nemo, and will (obviously) feature Nemo as he creates the Nautilus. Bill Marsilli penned the screenplay, and Disney is fast-tracking this puppy to film sometime this year -- presumably before the director kicks the next Terminator into gear.
I wouldn't be surprised if this means that New Line (under Warner Bros.) gets that remake cooking to compete with, or go alongside Disney's creation. Should it happen, it would be nice to two companies compete on something complimentary rather than repetitive (think Steve Prefontaine or Truman Capote). Regardless, McG is certainly making a solid name for himself, but what of Nemo's origin? Do you want to know, or do you just want him and the Nautilus to be a mystery of the sea?