Sandybridge i7 2600 will be faster than i7 9XX series. However, people who already have an i7/i5 atm should not bother upgrading. I am already reading some posts of people who would want to upgrade nevertheless. Spend your money on something else.
The hex core 970 and above will still be faster in multi-threaded tasks like folding, rendering, VMs, etc, DDR3 helps too, and far more PCI-E lanes.
If you also don't need the fastest, the current EOL chips are gonna be great bargains once SB comes out, and they are still future proof when it comes to gaming and less.