That's easy: they’ll create Photomator v2 and voila - you need to pay the full price again, because “this version has SO MANY innovations...”
Expecting lifetime updates with your lifetime license seems weird to me. That‘s not a realistic expectation.
but really, that's how software all worked back in the 90s, and it was fine. I bought Corel 5 in the 90s for $200 or whatever, and it worked great. If I wanted new features or other substantial changes, I was willing to pay for a new version.
The way I see it, there are 2 options: either you buy software "as is" and can use it forever, but you don't get free access to updates (or get them up to certain point of time), or you pay for a subscription. People who bought old versions of Pixelmator or Photoshop or 1Password can still use them (I have 1Password 4 on one of my devices), as long as the system updates won't render it useless.
It's the subscription model that is poison.