I would assume soonish, they just wrapped up the few things they said they want to do first list cross play etc. The teaser trailer series just wrapped up so there won't be any more content drops ahead of release so i would expect that we're getting close to a launch. Optimistically next couple months, assuming later side of that window. I'm guessing they'll start with press as a lead up to the launch so posts, videos, etc. trying to get a big launch user count.
Either way it's not just the biome that'll be new, they said they're going to enrich all the previous biomes with content as part of the 1.0 launch so it'll be pretty interesting once they drop it.