In reply to Stephen Hamill.

I just hope all the plugin and theme developers out there have ensured their products work with it before its WP core merged release.

This is somewhat wishful thinking. It won't happen that way in my opinion. Most plugin and theme developers I know of still wait and see what happens. "Gutenberg" isn't even in feature freeze mode yet...! Most developers will wait for a beta version of WP 5.0.0 and then see what they can do.

But: We still will see numerous plugins and themes not compatible when 5.0 launches! At best this would be a transition process taking months, at least. Also, a lot of plugins won't see compatibility at all as it would mean start from scratch and not every hobbyist or small (plugin/theme) business will have the resources for this I guess.