As Xan Lopez writes on his blog:
Lots of people still found the wrong extension version, or were not aware there was an extension in the first place, so their experience was not as good as we hoped. So for 3.8 we are just going to bite the bullet, and integrate adblock into the browser itself. Last week we took the extension, merged it into Web, cleaned the the heck out of it, and added a simple entry point in our preferences to control it:
The next step is to build a user interface tool that will allow users to set the blocking preferences like if they want the blocker to block ads only from a specific website for example.
WebGL support by default, better overview feature, integrated adblocking and so much more make me think that the Web is going to be a major improvement for the whole Gnome user experience in version 3.8!