Even $100,000 would kill it. If 1 sat (or even 100 sat) == $1 then the fees would grind the system to a halt. The fees would be so high relative to the amount sent, that it wouldn't be worth it. From an investment perspective 1 sat==1$ is a nice round number. From a users perspective, only being able to buy things divisible by 1$ is crap.
You are using your imaginative mind too hard. Here it is: Bitcoin going back to 1$ would definitely kill Bitcoin, even 100$.
I do not actually think that long-term in terms of Bitcoin's price. Plus, even if Bitcoin would reach $1,000,000, 1 sat is still less than a dollar.
Well, we'll cross the bridge when we get there. Oh no, wait, we definitely cannot arrive at such bridge. We are already walking dead by that time!
