In reply to Robert Trevellyan.

Access restriction will be a very important piece of all of this. Right now, we can do things like prevent Editors from editing nav menus so they don't break battle-tested layouts. (Of course, it would be even nicer if we had more granular permissions, so we could allow Editors to edit some menus and not others.)

If the direction of WordPress as a whole is moving toward basically showing the front end view of each full page and allowing everyone to edit everything, it will defeat the purpose of roles and capabilities. And I think even if roles and capabilities are taken into account, so some roles can only edit certain parts, it may become a very confusing UI - for one person to be working on a page and say "Oh, to change X just click here," and their neighbor to try to do so but nothing happens because they can't edit that particular content.