Delete any unwanted eververse armor and merchandise. After the update, all eververse gear will dismantle for shards and glimmer and bright dust will only be obtainable through Bounties.

The only thing they've confirmed is that Eververse armor in you collection when Shadowkeep launches will be available as Ornamentation for any new armor, and that armor will have a progression system to unlock additional mod slots on armor. Since they're keeping quiet on other specifics, I wouldn't be surprised if existing armor isn't converted to the new system, but some people are speculating that perks on armor you have in your vault [i]might[/i] help you to unlock the equivalent mod/perk in the new system, but I'm hesitant to believe that will actually be the case.