I've gone bigger rather than having to change it in a years time.
I don't know if I'll add more GPU's in the future (seeing how the land lies with the changes with SLI and high bandwidth bridges etc.), I am also unsure how many disks I'll add in the long run.
Not sure if I'll add a half dozen internal large SATA disks for storing some of the less intensive parts of my VMs on or if I'll get a Synology.
So I'm just covering all my bases, I don't plan on making major changes to this build in the foreseeable future apart from graphics cards, I'm sure I won't be able to resist swapping them at some point.