To this point, I would probably stop using the desktop version of the site if they nixed old.reddit.com.

Nowhere. People comparing it to Digg more than a decade later are wildly out of touch with the current state of the internet.

There are lots of interesting potential new homes popping up, including SaidIt.net, Tildes.net, Gab.com, even Parler.com and/or whatever Donal Trump has announced. Problem for all of them is their lack of critical mass. Reddit is slowly squeezing users and communities out to appeal to advertisers, but they haven't had their Digg moment yet. That would be something like killing old.reddit.com. Such a catalyst would cause a huge portion of their userbase to leave. So far, they've been too smart to do that, but I can foresee a bunch of new management entering the business after IPO and making those "tough" changes.

I'm also seeing various communities simply making their own websites. rdrama.net, for example, is surprisingly successful. kotakuinaction2.win is also doing quite well. I'm sure there are other, even better examples. At first I was resistant of this fragmentation, but I quickly came to embrace this reversion to the internet of yore. It wasn't so long ago that we would go to individual sites to discuss certain things. It's a relatively recent phenomenon that we've embraced monolithic communities for all of our media and social consumption. I don't think it's healthy, and perhaps this fragmentation is exactly what the internet needs right now. Less algorithm-generated outrage in the dystopian "news feed," and more user-driven experiences based on choosing which sites to visit. A crazy concept for many today.