Hey,
1) beyond 8GB is currently pointless. I can't say if that will change in the next two years but I doubt it.
2) VRAM beyond 2GB is harder to say. At your performance level if aiming for about 60FPS then there aren't currently any games which would benefit.
4GB may matter in the future for games designed with the XBOX1/PS4 in mind. We've already seen an example, Watch Dogs, which ran smoother on the PS4 but had major stutter on PC. The new game consoles can use about 5GB (shared) memory so at times we're likely to see 3GB of that as video memory thus a PC port can easily go over 2GB.
*Ask me a year ago and I'd have told you that more than 2GB on a laptop was pointless with only an 860M. Now, it's UNCERTAIN for future games.