In reply to John Rood.

Right now, people can use the ClassicEditor plugin, but this will cease to exist in the near future. At that point in time, people will have a couple of choices:

1. Commit full-time to the Gutenberg editor
2. Drop WordPress and change over to ClassicPress

But what is for sure, is that themes as we know it will go through a complete change and will be merely a stylesheet, per se. However, for ClassicPress, you won't see this happening because Gutenberg does not exist in it and themes will be what you see them as right now.