I believe there will always be miners for the foreseeable future when bitcon has resale value. The the sake of the argument, let's say all large mining farms are "on strike". What would happen? I don't know how much hashrate is from large mining farms, I assume 50%? The network hashrate will drop while difficulty is still high. Blockrate should also decrease to average of 20min/block. This would continue until the next difficulty adjustment.

There would not be a complete halt, solving blocks would be incredibly slow depending on how much hashpower is offline. You can still send transactions. Fee may skyrocket because everyone is fighting to confirm in the next block. It will not be nice