If your existing WinGate license had current version protection at 1 Jun 2016, it will be able to be activated in WinGate 9. Otherwise you will need to renew version protection.
If your existing WinGate license had current version protection at 1 Jun 2013, it will be able to be activated in WinGate 8. Otherwise you will need to renew version protection.
If your existing WinGate license had current version protection at 1 Jan 2011, it will be able to be activated in WinGate 7. Otherwise you will need to renew version protection.
Therefore you can use your license from a previous version in WinGate 6.0, and benefit from the many bug-fixes, and some new features (some of the newer features will require an upgraded license, but you won't lose any), that are available with the new version.
We recommend you request a free trial activation (handled in the activation client software downloaded and run as part of the WinGate installation), to check out WinGate 6.0's new capabilities.