Where has SE ever suggested that the current zodiac weapons won't further upgrade after the expansion is released? I'm sure there will be a brand new set of relics - but where did they say the current ones wouldn't also continue on?

When the weapons got the legendary Final Fantasy names (Excalibur, Apocalypse, etc.) I'm pretty sure that was the sign that they are here to stay. Are the hardcore grinders going to earn the final version of Excalibur at 2.51 and have a mere month or two to enjoy it before the expansion outdates it? I mean in three years when we are all level 75 or something - are we to look back and laugh at the puny level 50 Excalibur sword? Assumptions these might be - but I don't think SE would have granted the relics the legendary names if they weren't here to stay.

Doesn't make sense to me.