and was wondering how relevant it is today? Is 16 lanes still overkill for gaming? If I was planning to run Tri Sli should I go for x8 or x16? Out of all components at the moment? What is more than likely going to bottleneck? Cpu/Gpu?
Personally I think Tri SLI is overkill unless you have many monitors. A single good GPU like a GTX680 or a HD7970 can give you very high FPS even on demanding games.
However I've never tried SLI/Crossfire so I might be wrong.
About the bottleneck if you spend about the same amount of cash on both it's doubtful you'll have a noticeable bottleneck. Either the CPU or the GPU can be the bottleneck so just get both at the same level.
I don't recommend going above 2 SLI or Crossfire. I can say x8 is still really good now, and crossfire/SLI x8/x8 is still very good. If you plan Tri-SLI (not recommended) I recommend x16/x8/x8 (High end motherboard chipsets only though) examples are X58, X79, 990FX, etc.