Earlier in December Bloomberg reported that Apple plans to combine Apps for the iPhone, iPad, & Mac.
Although Tim Cook has previously stated that merging macOS and iOS won’t happen due to user experience issues, looking at the development of SWIFT which is Apple’s own programming language developed primarily for iOS this looks like a real possibility for third party Apps.
Not so much merging of iOS and macOS rather providing the ability for the same Apps to run on both iDevices and your Mac using SWIFT.
So Bloomberg is almost hitting the nail on the head however the key point they appear to be missing is; if you build an iOS App in SWIFT making the same App available in macOS is as simple as making adjustments to the code to include different frameworks such as UIKit for iOS and AppKit for macOS and making a few changes to the code. All of this can be achieved in a single project within Xcode.
This streamlines the development process and makes it much easier for developers to port iOS Apps to macOS and vice versa.
So looking into the future we should see those great apps such as IKEA Place and Things 3. However I don’t think such processor intensive Apps such as Final Cut Pro or Adobe premiere will be available cross platform like this in the near future.