It wasn’t specific in the 7/29 TWAB. It just says Console (with Stadia).
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ALL platforms will have crossplay. A console player will only encounter pc players by opting in first (inviting a pc player). Stadia is considered a console. Im assuming gen based matchmaking will remain the way it is now since bungie hasnt said anything, hopefully not and bungie tweaks it so 1 next gen player on a fireteam enables next gen only mm (instead of 1 last gen player bypassing next gen mm).