All good things must come to an end, even Windows 7. After January 14, 2020, Microsoft will no longer provide security updates or support for PCs running Windows 7. But you can keep the good times rolling by moving to Windows 10.
You can continue to use Windows 7, but once support ends, your PC will become more vulnerable to security risks. Windows will operate but you will stop receiving security and feature updates.
As long as your PCs meet the hardware requirements, should be able to upgrade to Windows 10, with a valid license.