This, from the Developers' Blog, is leading people to believe that this is the next and final stage of the relic line.
Considering how patches have gone so far, 2.0, 2.2, and 2.4 bringing ilvl increases and 2.1, 2.3, and assuming 2.5 bring intermittent gear to patch before it. Considering 2.5 is going to be the final stage of the crystal tower, I don't see the gear exceeding that of the final coil as that has been the pattern so far.
As for the relics themselves, the upgrade stages to match the coil patches seem to come out half way through the patch following the implementation of the given coil patch (halfway through a crystal tower patch).
Since 3.0 is upon is soon enough, it would probably be best for SE to ditch the current relics for an entirely new relic line in Heavensward, sure it's nice to still have your relic weapon be useful with all the work put in, it will make a nice glamour. But ditching them will make future relics more accessible to the entire player base.