Quote from: Fly-BTC on June 05, 2020, 02:49:08 AM

it might significantly improve the performance of their mining rigs but my personal question is, what will happen to the old mining rigs that they have? Perhaps, they have an option to sell it but I think it isn't the best option since no one will buy a hardware that is obsolete.

There are plenty of people who will find ways to mod the old hardware and sell it to individuals looking for a small start into mining as a hobbyist or for academic purposes. You can follow posts from Philipma1957 to know more about this.

Quote from: Fly-BTC on June 05, 2020, 02:49:08 AM

The next question I have is what will happen when we reached the last halving? no more reward will be available, then how about bitcoin miners?

Fee market. It will be several decades from now and if all goes well, bitcoin will have become the reserve currency for all others. Micropayments on second layer and on-chain transactions for their settlement + high-value transactions will provide the Fee.

Quote from: Fly-BTC on June 05, 2020, 02:49:08 AM

How about us, will we have enough hash power? Who will process our transactions?

The day bitcoin stops having enough hashpower will mean that the experiment has failed. Provided that the whole crypto-economy doesn't pivot to something worthy enough in the meanwhile.