I've heard Ocean mentioned before. Is it to replace Breeze?

It's clearly stated in the article.

KDE plans to tackle that through two already ongoing projects: Ocean and Union. Ocean is the new design system, while Union is intended to provide a unified theming engine across applications, Plasma, window decorations, and Plasma Login Manager.

I read it. It does not say if Ocean will be the successor to Breeze.

Finally, the theming in plasma is powerful but still quite a mess. The settings list a bunch of categories and one global theme, but I am never sure what settings can get saved in a global theme

Oxygen is still in KDE, so I doubt Breeze is going anywhere.

More reliable SMB mounts for the win!

Thank Ahura Mazda for that. I love Oxygen so much!

I don't think they are the same category of thing. Ocean is a design system. Breeze is a theme.

Edit: now I'm less sure. This seemed to say it is both a style and a "design system" which I took to mean a technical mechanism for styles, but now i'm less clear what they mean.

"Design system" is a way for designers to organize what they are doing with emphasis on structure and central definition of different components, colors, etc. This allows designers to create UI mockups more easily and programmers to implement the designs without guessing.

My guess is that that the new theme will be designed using this new system and then implemented using Union.

What about coherence?