Understanding the progression of the game...

[Niwashi]

You will reach level 51 way before you get the HW Quests

This is why I'm holding off on registering HW. I've already bought it (since I wanted the pre-order bonuses and know I'll want the expansion itself eventually), but I'm not going to register it until I'm ready to head to Ishgard. That way I can stay on-level with the content I'm doing and then head into HW as a level 50 as intended.

I wish they'd added a level-cap unlock quest (ideally on a per-class basis) so we wouldn't have to rely on not having the expansion registered as being the only way we could stay at 50 long enough to do the 50 content.

[Garlyle]

This is why I'm holding off on registering HW. I've already bought it (since I wanted the pre-order bonuses and know I'll want the expansion itself eventually), but I'm not going to register it until I'm ready to head to Ishgard. That way I can stay on-level with the content I'm doing and then head into HW as a level 50 as intended.

Register it now. There's no penalty for being overlevelled - you'll be level synced for old content, and there's a lot of experience to get to get to 60.