Philosophically, I'd like to see more non-connected link aggregation sites built around specific communities. I.e., there's no reason /r/askhistorians can't be www.askhistorians.whatever and serve the same purpose. HN is a good example of this kind of community-specific site; IMO lobste.rs is an even better example, given that it maintains a more consistent focus.
Community-specific websites have all kinds of advantages over "just another subreddit", including the fact that the community can literally own its own site, and build moderation policies and tools appropriate to whatever it feels its norms are. It can also throw up whatever barriers it feels are appropriate to keep out marauding trolls. (I'm a big fan of Metafilter's $5 account fee, as an example.)
It ought to be relatively easy to automate the process of spinning up such a site on a generic VPS. I'm very tempted to build something along those lines with Ansible or something.
Of course, in practice, the "one big site" model has tons of advantages in terms of barrier to entry, network effects, costs, discovery, and so on. So I doubt the idea would ever gain any traction. But one can dream. :)
(edit: fix wording slightly)