Aren't we going towards a dungeon deadlock ?

[Reynhart]

Old currencies stick around a lot longer than you think.

Well, no lowest tomestones stayed more than two patches. Philosophy was gone by 2.2, Mythology, by 2.4 and Soldiery by 3.0

Then poetics. Only after that Law will be gone, and by then the gear will probably drop from dungeons or be given as a quest reward, the way they also did in ARR (think darklight gear, for example).

I have the feeling that Poetics will stay, being lvl 50 tomestones. If you want to do the Zeta questline before lvl 60, you need a way to still gain tomestones.
But it's a possibility...still weird possibility... to allow lvl 60 tomestones before lvl 60.

As for DL gear, it was put in dungeons that only required lvl 50 to enter. We're already passed the ilvl170 mark in current dungeons.