One of the things I wish Apple would implement on the App Store is paid upgrades. Yes, I know there are plenty of other ways to monetise apps, but I happen to like the paid upgrade model. It's a proven model, and it still works.
Adobe doesn't have anything to worry about just yet, but if this trend continues they could soon find that Photoshop and Illustrator are no longer the go-to apps they once were.
Apple and some other developers advocate finding new customers to buy your app and make your business sustainable, but why do that when you have an existing user you can monetise? Sure, subscriptions are one way of doing this, but consumers do not want to subscribe to apps or anything else for that matter.
Given a choice would you pay for an app up-front or subscribe on an ongoing basis? I know which one I'd choose.
On the Mac, I'm going to continue selling my apps the way I always have done, paid up-front and paid upgrades after that. It's something I know my customers want, and it's something I'm happy to continue to offer.
Having said all that, I do think Setapp has a good chance of making app subscriptions on the Mac work. They have hand-picked a selection of the best apps available and offer the entire collection at a set monthly price. The value proposition for users is tremendous.
Oh, and Michael Love has a good theory about why we’ll never see paid upgrades on the App Store. Sadly, I think he's spot on.