This thread is from 2014, as is the issue you linked, so I wouldn't consider anything in it completely representative of the current state of CEF. Also, CEF hasn't used Google Code for some time, you should really be looking at the
Bitbucket issues if you want more up-to-date info.
As far as I know, your understanding is correct for current iterations of CEF. GPU accelerated content works, but there's still the GPU->CPU->GPU round trip for consumers of the rendered content.
Couldnt we get access to a texture used for rendering by a browser so content could be displayed without extra copying?
In theory, sure, but off-screen rendering is not really a goal of Chromium, so supporting this isn't as easy as it sounds.
The relevant issue for fixing this is
#1006, so I'd recommend watching it if you want updates on this issue. Unfortunately it does not look like anyone has worked on it for some time. The feature was implemented at one point, but the API it used in Chromium was removed before it ever got merged into CEF.