I agree. High-end audio manipulation will remain native, but I think for a simplified use-case (composition, lower quality renders) the browser is a good sell.
That and the tooling is almost here with MIDI.js[1], Web Audio[2] and Web MIDI[3] as a working draft.
[1] https://github.com/mudcube/MIDI.js/
[2] https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_A...