Do you have a reference for your rumor?
If you mean the article here - that just means that Apple will let developers release apps that can be used on both Macs, and Apple iOS devices - universal apps.
That would not indicate that you can purchase iPhone apps from the macOS App Store, although a universal app could be used on either, but not necessarily that you could purchase apps for your MBPro on the iOS App Store.
I would expect that a universal app would simply be available on both the iOS App Store, and the macOS App Store.
I don't think that you will be able to purchase and download an iPhone app from your macOS App Store, for example.
The rumor is that Apple is working on allowing for apps to be created in a way that they will work on both Macs an iOS devices without being separate as they are right now.
The underlying issue is that new Macs are Intel (x86) based while iOS is ARM based. So it'd be interesting to see how Apple plans to bridge the two architectures.