The big thing Aperture nailed though was photo-management workflows - it was never that great as an image editor. I don't see anything in Pixelmator that moves the needle in an Aperture/Lightroom-type direction by integrating photo management, which was the innovation Aperture and Lightroom brought back at their roughly similar original launch dates. Pixelmator is much more a photoshop alternative IMO.

I'd put money on this acquisition being used to improve the image editing experience in photos.app on iOS/macOS, just like Dark Sky was acquired and then used to improve weather.app, rather than any return of Aperture.