After Shadowkeep launches, Eververse items will break down into shards/glimmer/etc (not bright dust). So it you need/want to get bright dust now, you need to break down any unwanted Eververse items now. You can still earn bright dust after Shadowkeep, but it will be from different sources.
Here’s some information on it:
https://www.bungie.net/en/News/Article/47935