That’s essentially the plan. Our goal is to be as unobtrusive as possible while still doing things properly, keeping what works and reworking the rest, right down to the HTML DOM level if needed.
v2 broke a lot of user-created queries, scripts, and syntaxes. With this we’re aiming to modernise the entire CSS. That may temporarily break some themes and user styles, but we’ll provide documentation so users can rebuild their preferred styles and themes much more easily.
Here’s my “work in progress” document mapping the current CSS classes and structure, this will show where we need tweaks, fixes, or complete reworks. This serves as the current “as-is” CSS Structure Map.
The plan is to create a similar map for the future restyling, contributors and users will have a much easier time navigating and working with the CSS than they do today.
I also made a new Topic dedicated to this where we can continue the discussions and ideas about this topic:
And if we can’t deliver, we won’t PR it, and the user will still have at least a comprehensive & accurate structured CSS Map of the current version 
So it’s a win either way.