Ishgard Restoration isn't done. We've completed one small section of the zone. So anyone just getting there isn't going to miss out.
On top of this, I think it's a great thing the game has, it's part of a living breathing MMO, which is something we need more of, not less of. Something you can experience in the here and now. Something to tell fledgling friends years down the line how you helped build up this thing.
When we're done-done for good, I fully expect something else in the same style of play. It's not like there won't be future options to play.