The current relic has 2 distinct upgrades which consist of multiple steps for each. First you have Base Relic with a single step to upgrade it to maximum power (Zenith). Next you have Zodiac Base Relic (Atma) with multiple steps to upgrade it to maximum power (whatever 2.5 calls it).

This does not necessarily mean relics are coming to and end. What IS certain is that the Zodiac quest line is coming to the end. Relics may (and probably will) continue to get future upgrades post 2.5, just nothing related to the Zodiac Braves and the NPC Jalzhan.