each relic can be upgrade to the next level as what yoshi-p said he want to make them the most powerful wep. So i'm sure when the level is 60 or something they be a new quest chain and you use your current wep as the base to get the new one.

So far that what i know yoshi-p said he want to make relic the most powerful weps and the current PLD sword could become excalibur one day that one of the example.