My speculation is that this quest will get you a weapon that is on par with (just slightly better than) the current primal weapons. Then there will be an upgrade quest that make them even better.

I'm kind of hoping their goal is to have a line of quests that will keep upgrading these over the lifetime of the game. Use today's upgraded weapon down the road (when the level cap is raised) to do another upgrade that will continue to keep the weapon the best in the game for the job.