Apparently the delay is coming from casting issues as Brad Pitt who was supposed to play the role of harpoonist Ned Land turned down the role. Rumors said that Channing Tatum would replace him but it didn't worked either.
Personally i think it will be hard to make a better 20000 Leagues movie than the original one, even with what is possible in our days with special effects. Everything was perfect in 1954 Richard Fleisher's movie, the casting, the submarine design, James Mason as Captain Nemo, the look of the whole movie, etc...
Anyway, we'll see what happen, and in the meantime enjoy this great high-res file of a 1950's 20000 Leagues under the sea poster that personally i didn't knew...
Picture: copyright Disney