The mining farms that have invested a large capital won't let their farms to shut down because of that. They will keep themselves on the trend unless they can't keep and take the expenses anymore.
Agree, these big mining farms would be the last to stand until the last Bitcoin is mined. This expense is just a one time upgrade in 4 years anyway, and I guess they could easily handle that, but then again the total amount of expenses is a pain in the a** lol
There must be sort of savings dedicated for future upgrades.