If the options are expiring, the company can choose to 1) foot the tax bill for the employee via payment or buyback, or 2) reissue the options as RSUs. Only some companies make that choice, but it's certainly legally possible to work through the 10-year legal expiration for ISOs.

I know this from experience, but here is a reference with good detail (no affiliation): https://www.founderscircle.com/10-year-expiration-of-incenti...