Do you think countries worldwide will ban Bitcoin mining due to environmental concerns?
The better question to this is, can they and will it have lasting effects and will enough countries do it? And the answer to this is no.
If mining is banned, do you think Bitcoin will switch to PoS?
Maybe some altcoin will, but not
BTCWill it still survive being a PoW cryptocurrency?
1000%
If not, why?
You can check out the technical development section, there was many great answers to this.
Dont buy into the FUD guys.