I think it'll just go down in history as a well meaning, not nessarily an ill fated attempt to change the world though... I don't think a concert of any kind can do more than give awareness of the issue; in some cases proceeds may go to the cause but that normaly doesn't fix the problem in its entirety.
Now awareness can/could change the world over time, it won't be instant though. Many people look at others or organizations who want to change something and ask themselfs the question of "did it work" from a current time perspective; if they see no imediate change it's deemed a "failure". If you look 10 years from now, and people are talking about the concert and doing what they can to help; then yes the concert did change the world.