Maybe the Original Subs won't be Returning!!
A friend of mine, whose father is an imagineer for Disney who told me the monorail would go down right after the 50th about 4 years ago.
The father told me that the subs will not be running on diesel engines anymore but instead an alternate source of energy. I did not want to further press him with the question. But from what i got out of it, unless they totally altered the yellow subs with new material, its not looking like the old subs will be coming back but a new submarine equipped to handle something but diesel.