I feel like it's saying we're going to first go down under the planet to confront Hydaelyn and get an explanation for everything (and possibly find out what the Sound is), then go up to the moon to destroy Zodiark. Future generations hating us could be because we destroyed the moon and they don't know why, and resent us for such an act of destruction. The resolute man could be Louisoix, which would fit in with going to Sharlayan to uncover more mysteries about Hydaelyn and the Lifestream.