There are plenty of people mining with GPUs who have "free" electricity. As long as they get something out of mining it will continue. Difficulty must be 100x or so until GPUs are completely out of question.

Shutting down the GPU farms will be gradual as different countries have different electricity rates, the difference in electricity rate can be 10x between to countries.

Major movement in BTC/USD price can make things completely different, GPU mining can end next week if there is a huge crash in BTC price, or it can continue through this year if BTC gains value rapidly.