The entire area around DLR was rezoned in the 90's so that it could only be used for theme parks, shops, restaurants, hotels, and other tourist-related things. This is when the area began to get cleaned up. Then there was this timeline of events regarding
these parcels at the center of this map East and across the street from the Toy Story parking lot:
Late 2006(?) - Developer SunCal proposes to build 225 low-income apartments (and 1275 market-rate condominiums). There was was originally a hotel component that was later dropped. I don't know when the original proposal happened, but probably around late 2006.
Spring/Summer 2007 - Disney sues the city of Anaheim for this first time in history to keep residential development out of the resort district. Proponents of the development frame it as Disney being against low-income housing.
October 2007 - DCA makeover is announced. I think there were also noncommittal commitments from Disney around this time that a third park would be built on the Toy Story parking lot in the mid-term future (which was still strawberry fields at the time, I believe). Disney makes it clear that it will be investing major money in the resort district in the future.
By Christmas 2007, the project was dead. Keep in mind, at this time DCA was still a loser of a theme park that no one would be seen in. Disneyland was spruced up for the 50th, but hadn't (still hasn't) seen a big splashy expansion in some time. From the outside, it may have looked like the resort district was as big as it was ever going to get. Plus, these parcels are on the edge of the resort district next to I-5. With the announcement of more than $1B of investment and wispy promises on the wind of a third park on a plot of land right next to the proposed development, Disney reasserted its economic hegemony over the area. I don't mean that in a negative way, either: they showed that they weren't done investing in the resort district and that there was still growth to be had and good reason to save the land for more tourist-related development. Personally, I think the resort district is actually pretty small. I don't think it's a big deal to keep residential development out of that small area.