Killing old.reddit.com would probably be their final Digg moment for me. Maybe they'll manage to keep the bulk of their users and keep some husk of it's former self going for a long time, but I'm gone. I suspect many others will join. The quality of content has been plummeting for years anyway.

Too bad there's no clear successor this time.

Yes the discourse and content quality is quite poor, so much so that I quit using the site completely in the last few months. To be honest I don't miss it at all, so...