Not sure how to feel on this one.
I use Pixelmator a LOT so on the front, Apple acquiring, tighter integration into Apple's silicon, bigger dev team with larger funding will always be a bonus. It does worry me though that Pixelmator could get "stripped" of it's good bits and those integrated into something like Photos or some other Apple branded roll across every device in a dumbed down kind of way app.
Pixelmator was the first app I bought when I moved over to Mac as the alternative to buying Photoshop and to this day remains my best spend in App store.