That would be a nice outcome. I’ve been missing a replacement for Aperture for years. I’m not a professional photographer, but I’ve got more than 30 years of photos inside of Apple Photos. Some old school scans or Photo CDs, some RAW from underwater (Photos does a poor job here), and a ton of iPhone photos.
Bringing a more premium experience to Photos would be a great complement to how you can already shell out to Pixelmator while editing photos.
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.