I'm pretty sure reddit will be ok. Even if it changes into something else.
I am still going there for some niche subreddits (r/blender) because there are so many users compared to here (where I have now started /t/blender). If you are in those smaller niche subreddits you don't get any of the shit compared to say r/all. I do hope the smaller tribes here can grow though so i can totally cut off from reddit.
Yea, this is what digg didn't have - established micro-communities. I can't imagine /r/blender, /r/learnprogramming or other such subs to ever feel the need to move unless something much worse happens. Or, of course, an alternative providing such a significantly better experience than the existing option, but as the main influence on that factor is the level of activity in a community, it's hard to imagine how that would happen.