PCI Express 3.0 will not piss you off.

The concept of the next PCI Express version could be potentially distressing to people like us, but thanks to Jeebus, it does not sound too bad. So prepare yourself for a heaping helping of good news!

3.0 will be backwards compatible with 2.0 and will use the exact same slot design that we have right now. 2.0 has a transfer speed of 5-gigatransfers per second, whereas 3.0 can transfer at 8-gigatransfers per second. The specifications for 3.0 will not be done until late 2009 and testing will be completed in the second half of 2010. Therefore, motherboards with 3.0 will not be available until late 2010 or later, so we won't "have" to upgrade our motherboards for a while.

Engadget article.