Wow, the amount of negativity here is awful. I looks like most commenters have not even read the article...
First of all, the HN title is not the title of the article. HN mods, please change it to reflect the actual title of the article.
Second, to me this does not seem as some attempt by Google to actively block Adblocker extensions. They are proposing a change to the API (Manifest) to no longer allow manipulation of content, which I think is a good thing from a security standpoint. They also propose reducing the number of content stripping rules to 30k. Now, I'm not familiar with add-on development, but this sounds like a constraint that was implemented for performance reasons. This constraint will break add-blockers in their current form, but there is no reason for me to believe that this will make content filtering impossible.
It is also clearly stated that the V3 manifest is in early testing phase. Nothing here is set in stone.