You only need 8GB for VRAM if you are playing at 4K or high settings at 1440p. The only thing I've ever seen that used more than 4GB @1080p was the Unigine Super Position benchmark at 4K.
Yeah I play at 1080p with 4 GB of VRAM and while I don't try every game out there or always run the latest stuff by any means, I can't say I've had any issues.