4chan is barely that edgy anymore. the guys who are going to shoot people all went to 8 or other places. Any talk of killing people is just met with 'hello fbi' even on /pol/. The only illegal content on the site is what's posted on /tv/ sometimes and nobody really cares about the occasional illegal image that gets deleted within a minute. It's possible that now that 8 is down they go back to 4, but idk, the way the boards function over on 8chan you had month long threads and a much more extreme core userbase with much less spam, so it allowed things to get more real.
I think you're right in the long run that 4chan will get shut down, but something is going to have to directly link it to an event like el paso I think.