I'm not going to buy hydro power is anywhere near fully tapped when so many rivers are free flowing. Wiki says the IEA report claims there is 75% undeveloped in North America and 82% undeveloped in Asia. So it's already the #1 renewable with less than 25% developed. Africa is basically untouched with 95% undeveloped. These are using current methods, and true using just those methods wouldn't rise to my claim of filling the future world's entire needs, but it could probably cover the current needs.
This is an interesting study on the total potential, but the final conclusion is only maybe 4-5 times "current" capacity is possible.
https://gigaom.com/2011/12/23/how-mu...gy-can-we-get/