I think, and dare I say it, this is where the mention of the dreaded 5th gate comes in. Disney is doing a lot of demo within spaces that already exist. If I'm going the wrong way from @drizgirl is, then I apologize, but not everyone likes Star Wars, Toy Story or Avatar. There are people who are currently holding off on Disney vacations until some of these lands (mostly Star Wars Land) is done. So you're going to have a pretty big influx of people at that time, in addition to normal vacationers.
Anyway, let's get this thing back on topic...
Exactly that. And even worse on the west coast where SWL is going into an already overcrowded DL park. There's no way there is enough ride capacity coming there to offset the huge increase in crowds it will bring.
Slightly different on the other coast, but similar concept. And I agree that many have put off trips until the "new stuff is done". I think the increases in crowds will be greater than the increase in ride capacity.
Time will tell.