Well, this came completely out of left field.
As someone who relies on Pixelmator daily since they shipped 1.0, I am happy for them, but sincerely quite afraid Apple will botch this–their track record with acquisitions is dismal (just look at how they gimped Shortcuts even as they folded it into the OS, how Dark Sky essentially vanished, and what happened to the AI startups they acquired).
To be honest, I would be surprised if it still exists a year from now, and even more if it keeps shipping new features.