If I may hazard an uneducated guess:
Shanghai, then Shanghai again, then Anaheim. China's economic boom has made park trips affordable to literally hundreds of millions of people, and even though a Disneyland trip is mainly something for the richest percent of people, that's still a number in the millions. Barring any crackdown on Western culture in China, the Shanghai park soon won't be able to meet the demand (or rather, a second gate will become a very profitable investment), and the park may be expanded into a resort of some sort. Cue a second gate and a waterpark. Meanwhile, Disney will eventually find the cash to buy one of the hotels next to their California parks, as the buildings age and their value goes down. With some trickery involving more compact parking garages (since open-air parking lots are woefully inefficient), there could be enough land to fit a small-sized park - for instance in the area east of the current park, in the triangle between the existing park and the highway.
As for entirely new Disney parks in entirely new markets... probably won't happen for decades. When it eventually does, my main bet is on Mumbai, India. Possibly even later, somewhere in or near Nigeria or Ethiopia - both countries will have more than 200 million inhabitants by 2050. Time will tell if their economy as well as their population may warrant a Disney park. After that, most of the world will be somewhere in the "catchment area" of a Disney park. Once Africa and West Asia are covered, the next entirely new park might as well be on the Moon.