As XRP is more suitable for payments than IOUs, it seems that IOUs would become only a secondary feature, and so it seems unfair to call this system Ripple.
I fully understand that this kind of reasoning has a kind of attractive logic to it, but I think that's an extremely unlikely scenario. I could have made a similar argument in 1950 that people would soon abandon fiat currencies and switch to gold certificates. I can make a similar argument that Bitcoin will make fiat currencies obsolete. Sure, that might be the endgame in the far future, but to focus on that endgame *now*, rather than the many decades of work we have to get there, is navel contemplation.