With the imminent release of V-Ray 5 for 3ds Max this is the last time that users can upgrade their V-Ray 3 licences.
Currently V-Ray 3 users can upgrade to V-Ray Next, however as soon as the latest version is released V-Ray 3 will go end of life and the upgrade path will be closed entirely. Which means the only way to get the latest version will be to buy a new licence.
Only purchases of V-Ray Next made between 29th April and the official release date will be eligible for a free upgrade to V-Ray 5, meaning that any current licences of V-Ray 3 will need to be upgraded twice to get the new version.
However, V-Ray 3 licence holders will be offered a 20% discount on new licences of V-Ray 5.
It’s also likely that V-Ray for Maya (which is now in public beta) and V-Ray for SketchUp will follow suit at a later date.