I read Disney scrapped plans a handful of years ago in Newport Beach and most recently they were clearing space for another hotel/resort (no confirm that it would have DVC tho) at Downtown Disney next to the Disneyland Hotel, but some articles read that the City of Anaheim and Disney had issues and couldn't get on the same page.
but this at least are hints that Disney wants to, so hopefully 1 day during our lifetime!
The City of Anaheim apparently has a law that Disneyland can have no more than 150 timeshare units on the current Disney property. And they count a 2 bedroom lock-off as 2 units. 1 Studio and 1 one bedroom, even though Disney counts it as one unit. So Disney says Grand Californian has about 50 units, but Anaheim says 75 units.
Then Disney had a deal worked out to build a new hotel, which MIGHT have had some DVC units, and do it on the west end of Downtown Disney. They were going to get a hundred million or so dollars in tax breaks from Anaheim, to do so. The room taxes for the next 15 years or so would have been split between Disney and Anaheim, then ALL revert to Anaheim after that. But Anaheim got greedy and said that since Disney moved the entrance 150 feet towards the east, to include the monorail station, that it was now not what Anaheim had agreed upon, so the deal was off. So now Disney is NOT building that new hotel and Anaheim is getting $0 dollars in income from it.
Zoning Code, but zoning code is like a law, really. You play ball with it or no permits.
The restriction is within the Disneyland Resort Hotel District, as it is called in zoning documents. If Disney wanted to build away from the current hotel zone and DS in what is known as the Anaheim GardenWalk district, they probably could. But lots of reasons why they would not bother.
If you are a super nerd, the whole thing was adopted in 1993 and you can see some of the developments allowed for that occurred, particularly Cali Adventure, in the zoning plan: https://www.anaheim.net/1017/Disneyland-Resort