Keep at least one of each until TTK drops. Your inventory/vault are added to your blueprint archives at that point.

Besides Bungie stating you shouldn't dismantle anything before TTK, I'd also suggest not doing it because it seems highly likely that the weapons will break down into a different material after the update.

I remember people talking about things they should save before the Taken King, and I might as well ask--since they're changing up this whole Exotic thing, should I keep the VMM's I get until September, or just delete them now? Are they going to unlock anything special/new if I hold onto it?

I've already got one for each character, and I'm probably going to get more, too.

If you have any un-upgraded or not-unlocked exotics that are duplicates I'd say it's safe to dismantle them, I already did. You'll want to keep one copy of each exotic regardless of how upgraded it is (or even how good, because who knows how balancing will go) because that'll unlock the ability to get it again whenever you want for a cost of one exotic shard and some currency, and for certain exotics you'll be able to get a new version with different perks and apparently a higher maximum attack value.

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