If the choice is Gen 3 or Gen 4, I would have to call it Gen 4.
There are enough differences between the two that it could be important when discussing technical issues. Lighting (and power consumption), transmission, clutch issues are significantly different. I was happy with the 3.5 moniker because the changes aren't earth shattering or an entire rework. So, Gen 4 it is, if only for technical discussion!