No-backend cuasi-static would be a new era. There is no reason for a dynamic CMS on sites that are updated twice a month and maybe reach 50k visits/mo; I am sure the vast majority of WP sites out there are of such nature.
I'm sure the vast majority of WP sites have been built for a paying client.
I would love to see a user-friendly universal app for managing static sites (Jeckyl, Docpad) that is something someone of my Mom's tech capability could use. (and let's be honest, WP itself is sometimes "way too much")
They want a friendly easy way to manage a complex case management system, but they don't understand how some of interconnected relationships work between the data they want. So trying to cross that chasm, of explaining what they actually want implies for the data has been miserable. Somethings just aren't simple :(
Using either of the above, you'd reduce the latency and increase the through-put of WP to the likes of hosting a simple HTML page on nginx.
The picture gets a bit more complicated with the back-end admin area, user logins, sessions, dynamic page parts, etc. And there are ways to either handle it or just bypass the caching layer for it, but for handling reader traffic, caching is the key regardless of which CMS you use.
Also, the more visits, the less of a need for a dynamic CMS.