your commercial v4 licenses are perpetual, and will be always yours.
Now you have some possibility to update your licenses to v2020.
If you want to use new versions, you can purchase an annual Enterprise subscription update for 199€, but at the end of the annual maintenance, your licenses will go back to v4:https://render.otoy.com/shop/upgrade.ph ... C67-UGAA1Y
if you want to upgrade also your v4 perpetual licenses to perpetual v2020, the upgrading path is more expensive, to know the price, please visit the following link:https://render.otoy.com/shop/upgrade.php
At the end of the annual maintenance, your licenses will stay to v2020.
Note that all upgrade paths are offering you the possibility to use any kind of Octane DCC plugins (including C4D, or Maya and OctaneX), and also the ORC/RNDR Octane Render Cloud services (render credits need to be purchased separately).
Happy GPU rendering,