I think some saas will die, but having common cross industry/cross company softwares being managed by a seperate entity would make logical sense for the broader world(better design, seperation of concern?), even if arguably they could create their own version of that company.
Case in point, PM management software (Jira), might be a very easy tool now for any company to make(a very naive stand, but in a world of ai not far fetched to argue), but managing and maintaining that software is still a chore, and it might not be in the interest of everyone to spend their effort on it. They might still prefer paying for it. Now, the product itself might die and some other product might take its place, but still that new product would be an individual thing. Atleast that's what I think.