In reply to Mac.
The plugin is now the development version of the Editor.

Its development happens to be way faster than this of Core, so it is separated, which makes sense in my opinion. Every time a new Core version comes out it is decided which version of Gutenberg and which fixes etc. go into Core so Core always has a stable version of the Editor.

Yes, you can use the Gutenberg plugin and it will replace then the Core version of the Editor. I would only recommend this for testing or staging installs, though, not for Live.