Generally speaking the hash rate will drop very hard because of negative ROI of mining (let's say $60?), at that point the bitcoin blockchain network might stop processing any transaction.
Then no one can send or receive any bitcoins anymore.
That makes no sense to me at all. I was here when BTC was worth pennies and it worked fine. If mining becomes unprofitable then miners shut down some of their mines. This is how actual mining works also. It is also how this system was designed. You may want to read "the white paper" by Satoshi Nakamoto. It may clear up some of your confusion about how bitcoin works.