I find it funny that people think Disney truely Cares about crowd size. Disney wants there parks to be crowded, it allows them to make more money and then also make "hard ticketed events" That allow them to manipulate crowd levels for the guests paying them extra money to do so.
Yes Disney is getting more and more crowded, yes even for people like myself who like to go several times a year, we notice it. Do the crowds bother me? Yes and no, It bothers me when people run into me, I am 6'4 in a kilt so I know im not hard to see, but at the same time it doesnt bother me because I can sit back with my wife at a Bench or near the Main Street Train Station, and just people watch.
Its a vacation that people are willing to pay a large amount of Money to go on. Adding or Subtracting Rooms, doesnt really effect the crowd size. Disney has manipulated the schedule with Wine Fest, and Garden Fest, and the Holidays to pretty much make null and void the traditional less busy times. In saying that I still love April- Early May because it can be one of the few low crowd times without the super Florida Humidity.
Regardless though Disney wants its parks full and crowded and it wants its resorts full. Adding more rooms only allows Disney to accommodate more guests in the bubble, what truely effects the number of people in the Parks is the number of people who want to visit the parks and can afford it. Adding rooms does nothing to effect the amount of people who can afford a Disney vacation. Its not like Disney magically building more rooms is going to increase a families overall Take home pay. All it does is allow Disney to make more money by making available more rooms with more options for people who were already coming to Orlando to decide if they want to stay at.
Would I love a 5th Park, most defiantly, would a 5th park help lower crowd levels yes for awhile, will more people come because there is a 5th park, sure the once and a lifers will have another reason to become a twice or three time in the lifers. You can not blame hotel rooms for crowd levels. If anything we should be blaming Disneys marketing team for doing to good of a Job in making people feel like they need to bring there kids to Disney to be "good parents" or making International guests want to spend alot more money than us Domestics do to visit the US for two weeks and hit Disney and Universal. The number of rooms is just a scapegoat.