Feels like "what is the future of the word processor" but with some weird expectation that you're expecting to see leaps and bounds.
Look, FWIW, my favorite music making "stack" is
- Fruityloops (as in, sure I'll use FL Studio but it was pretty much solid for me when it was called that)
- Sony ACID. Still unbeatable to me for quickly layering/previewing multiple tracks of loops
- Cool Edit Pro/Adobe Audition. Still much nicer than Audacity. I don't know why Audacity remains so popular, it's way clunkier than the above
Ableton/Bitwig are also fun to play with and I could see them being indispensable for some, but what more do people need that you couldn't theoretically get "incrementally" or "with plugins?"