In reply to Chip Bennett.

Chip, to me it is interesting how new themes will co-exist with "classic" themes on WP.org as for at least 2-5 years there will be users still on older WP versions or on newer versions, but with Classic Editor installed.

It looks that theme authors will be forced to post modern iteration of their themes as new themes, otherwise I do not see how in practical way theme author can serve "classic" theme to users without Gutenberg and "modern" theme to users with Gutenberg.