In view of how AI is changing graphics tools, my guess would be that Pixelmator's pay-once business model didn't bode well for long term competitive viability.
We've already seen Affinity switch into releasing a "v2" after years of updates, and on the other hand hobby apps like LightTricks get far more out of their subscription services, despite being a consumer grade template-based app.
As for how it will be run. I'm guessing that Apple will just be their backer like they do for Claris. I don't imagine a MacPaint style app returning to macOS, but sharing code between the two to enhance mark-ups, the photos app and the like seems likely.
For random conjecture: this may also mean Pixelmator grows into the AR space.
We've already seen Affinity switch into releasing a "v2" after years of updates, and on the other hand hobby apps like LightTricks get far more out of their subscription services, despite being a consumer grade template-based app.
As for how it will be run. I'm guessing that Apple will just be their backer like they do for Claris. I don't imagine a MacPaint style app returning to macOS, but sharing code between the two to enhance mark-ups, the photos app and the like seems likely.
For random conjecture: this may also mean Pixelmator grows into the AR space.