I don't have a source beyond what I have heard in LS chatter.

There will be a new 'relic' weapon available in Heavenward. The current Zeta is the last form of the zodiac weapon arc (or there is 1 more upgrade for it, this discussion was before this week's patch, so not sure if the 'one more upgrade' refers to Zeta phase or not).

They said those who have completed their zodiacs would not be forgotten, and given a 'head's start' in the new relic weapon progression.

Wish I had the source on this, as the LS chat we were having pple sounding like they were reading it directly from a dev note or letter. I think there is something floating around on this.