Russia dropping the USD as a reserve currency doesn't mean anything, considering Russia doesn't have much sway in that regard. I doubt you would see 5k Bitcoin because of that.
Correct, they don't have much USD. It is the idea that is so dangerous! Domino effect! This is why Iraq was attacked, they wanted to sell oil for EUR which was a massive threat to USD superiority and USA business model. So they got a lesson.
Now trouble with Russia is they got nukes, so Uncle Sam will have troubles invading them.
Russia could start selling oil/gas for crypto, which would mean $5000+ Bitcoins and massive threat to USD/USA. They won't do that IMHO because the ruble is fiat, and fiat is power over people, but you never know. Selling oil/gas for EUR would be enough to devalue USD quite a bit.