Tell that to the people who relied on Google Wave and Wunderlist. Or to the people who said "Linux will go the way of every other hobbyist OS" in 1994. I knew several orgs who were devastated when Atlassian shut down Hipchat.

If you want the only guaranteed probability about the future: its that most predictions about the future are wrong. Everything dies eventually; the things you least expect last longer than you expect them to; or sometimes much shorter. I do feel pretty confident that both Github and sr.ht will be operational tomorrow. But, not 100%; and even less than that next Tuesday; and even less by September.

Actually, Github has had 12 public incidents since May. So... maybe I shouldn't be so bold with my predictions about Github's operational status.

When people say "something is unlikely to happen" what they really mean is: I really hope that thing doesn't happen. Me, personally; I hope both Github and sr.ht continue to see success. As you say; me choosing to pay Github $5/mo won't change anything for the better or worse; but paying that to sr.ht, now that impact is much bigger. If you distil it down to the manifestation of your own hopes: I think the choice of who to support is obvious.