Steam boat willy doesn't bring in any $$$. When one of the early classics that still sells (Bambi, snow white, etc) comes up please believe an extension is right around the corner
And they do sell steamboat merch, or have in the recent past:
https://www.lego.com/en-nz/product/steamboat-willie-21317
I don't see it going into the public domain. Steamboat Willie should have entered public domain in 1956 and Disney keeps winning.