Not really worried about nodes, more so miners
Bitcoin has no failsafe for sudden hash-rate loss. Difficulty only adjusts after 2016 blocks, no matter how long that takes.
Probably would have bigger things to worry about...
Discussion
I have considered this. If 99% of the miners go offline and we are mid change, a week become 2 years. But prices to transact skyrocket. Also so much incentive to get miners back online so people would find a way.