Yeah, I agree, I think the "next" major 'Eternal September' if you will was around the 2010's give or take after Smartphones became far more common and everyone had insanely easy access to the web. A lot of web traffic is insanely on mobile, whereas before it was not, and it was a mess (remember those awful .mobi domains that you would be redirected to, BUT only the home page, so whatever content you wanted was gone, good luck finding it now since you just hopped off Google!).
The 'Eternal September' was actually pretty early on--basically pre-Web to Web 1.0. I had a Unix workstation with a Mosaic homepage which basically had links to all the sites I found interesting. I agree that something happened with mobile/social. This post is more about the Read-Write Web (I think that was O'Reilly's term)/Web 2.0 era--which was between the two.
