Even though PCI Express is still barely introducing itself to the market as a whole, with very few cards aside from video and ethernet available for the interface, the company behind it is getting ready to approve their 2.0 revision. PCI-SIG, the company behind both PCI and PCI-Ex, has introduced an RC for version 2.0 that introduces things such as a doubling of the theoretical bus bandwidth and a new cable length specification, providing distances of up to a ridiculous 10 meters.
Supposedly, the final specifications are just a few months away. The article doesn't mention the interface itself or about backwards compatibility, nor about future adoption of PCI-Ex 2.0 over existing PCI-Ex. However, if you were buying computers when the first Intel boards with the PCI interface started showing up, you'll remember that nearly the same scenario was played out many other times, as PCI began to supersede ISA and other connectors.