I'm pretty certain the answer is no but I'll ask anyway.
Let's say that attendance at WDW continues to drop and Universal builds 2 more parks and have 2 great resorts (enough to plan a 2 week vacation around) and it comes to a point where families will have to pick between Universal or Disney as there won't be enough time to do both.
Could Disney and Universal ever team up to make a joint ticket for both resorts?
I know that Disneyland used to have a friendly relationship with Knotts Berry Farm but over the past few decades, Disney have burnt all the bridges with local competition.