Color me skeptical, but it seems like bullshit to me.
The newspaper article has basically one source. The Wikipedia article dates from the day the newspaper article was published, and only has the article (and a reprint) as its sources.
Interesting. I think you're on to something here. The wikia stuff seems to have been created in August 2013. The subreddit /r/cicada appears to be 11 month old, but the article implies that Eriksson discovered it in the beginning of 2012. And it's virtually empty. Hmmm...
Edit: oh well, nevermind. A google search between 1/1/2010 and 1/1/2012 returns plenty of stuff, for example a discussion [1] on the xkcd forums from January 2012.
It doesn't take much digging to find sources older than that, really. ;) For instance, you can check out my own post about it at http://www.clevcode.org/cicada-3301/, originally written mid-January 2012. The oldest comment on the post is from 2012-01-14. There were articles written about this back in 2012 as well btw.
PS. I'm the Joel Eriksson that was interviewed for the article in question.
The "original image" linked to on this site also does not contain the plain-text "TIBERIVS CLAVDIVS CAESAR" etc. described, according to my hex editor.
However, the "original" PNG image linked in the article does not contain the plain-text described in the article (at least, not visible in my hex editor). The pixels do contain some artifacts in the lower bits, though.
The newspaper article has basically one source. The Wikipedia article dates from the day the newspaper article was published, and only has the article (and a reprint) as its sources.
http://uncovering-cicada.wikia.com doesn't seem to have any activity from more than 6 days ago.
I'm really not a cyber-sleuth like the guy in the story, but the first two pages of Google didn't show anything from before 11/26/2013.
I'm sure the puzzles are engaging, but this looks like fake buzz.