One interesting question will be about copyrights. There are other melody-making programs but I'm not aware of anything catchy or worth registering with the U.S. Copyright Office being created by them. It costs $8.50/song. I've registered all 60 melodies I've posted so far since they all required my creative input, but with further advancements, the creative input will be reduced to cherry-picking best melodies. Eventually, a high enough percentage of the melodies created will be good enough that somebody will attempt to just register all of them. It's unclear whether they'll be judged as worthy of copyright protection under current laws or if these laws will be changed.
Another very interesting question is what's the number of "good" melodies. We could define this as being rated by random people at a level equivalent to an existing melody from a database (e.g. Hooktheory's) that they're not familiar with.