Q: Even the highest end cards aren't that limited without it. So when will it truly be necessary?
A: Whenever graphics cards actually start getting bottlenecked. It's hard to say. At the rate that graphics cards are going, especially with these dual card configurations, it's probably not that far away. So basically, if I was buying a new motherboard, then I would probably get one with PCI-e 2.0. But if you see a motherboard that's a bargain, or if you aren't in the market for one, keep what you have as PCI-e will still be sufficient.