Yes, Virginia. In 2000, Disneyland did announce intentions to build a third theme park with initial construction beginning in 2003 and completion by 2010.
They even had a website about it… here is what it looked like in 2000:
https://web.archive.org/web/20000817041730/http://www.thirdthemepark.com:80/
It has some before and after images of the area around the resort that are stunningly different. This is what was going on leading to Disney’s California Adventure opening.
Several things they mentioned did make it to the resort, but not into a third theme park.
Until next time…