I do not advocate a 5th gate. I think many of you have valid points that a 5th gate is not the best use of money, time and resources. But to be so dismissive of it is ridiculous.
If Disney had say 6 billion dollars (using one estimate of Shanghai
Disneyland) to spend in addition to what has already been earmarked for DHS and Animal Kingdom. I would rather have that be used to heavily re-imagine Future World and potential re-imagine all of Epcot into a more timeless, easily maintained park. Adding a few pavilions and the like and Epcot is good to go. Also building more resorts that are not solely DVC. Also adding another Pixar/Wreck-it-Ralph/Big Hero Six area to DHS and build over the north end of Rivers of America and behind Liberty Square like they are doing at Disneyland.
That would be 5 new or completely re-imagined areas to already existing parks that could dramatically increase capacity/time usage and take the pressure off of Magic Kingdom without building a 5th gate. But Disney could have spent all that money that went into Animal Kingdom to development of Epcot 2 decades ago. Or not rushed DHS. Or you get the picture. Nothing drives interest and excitement like a new park. So we might end up with 4 half parks and one Magic Kingdom by 2030.