What I would expect to happen to Irish paper ABC is that it would evolve extra features, becoming something very different. That's happened with ABC I've written myself: it's quicker to write a triplet or phrasemark over the line (as in staff notation) rather than in it.

There have been many text-based notations over the millennia and they've all done that. A harpist friend of mine says the notation system of the Ap Huw MS is perfect for her instrument and brilliantly readable - if you're not an early harp wonk it looks like feeping creaturism to the max.