After the halving, many ASIC models will either become unprofitable or give very little profit. And in order for large companies to use all the power for maximum profit, they will turn off thousands of old ASIC models.
And what will happen to these ASICs next?
Will they be sold to other countries or disposed of?

If you want to buy a used ASIC now, don't do it. After holving there will be a big discount on such ASICs on the market.