As said above... 3 years from now you would have most likely upgraded platforms. Since only the top end cards will be able to actually use that bandwidth, the people that buy top end cards are usually upgrading at least every other year.
The point I try to make to people is this: If PCI-E 3.0 is included in the hardware you buy, great. If not, don't worry about it. Don't make PCI-E 3.0 a primary decision maker in the hardware you choose to buy.
I would not have upgraded from Sandy to Ivy, for the sake of PCI 3.0 or anything else new in Ivy...
However, as I don't upgrade that often, but want a very big upgrade when I do, including graphics, PCI 3.0 in a new machine, of course...