Don't complete it until the DLC releases!!
Planet Destiny confirmed that when you turn in an exotic bounty after the release you will receive the version 2.0 of that weapon!!
You won't need to waste your shards to upgrade it!
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I did this with Thorn this AM. Starts at attack 302. I sharded my fully maxed Thorn for 2 exotic shards. Beats trading it into Xur.