Current ZigBee Certified products based on ZigBee Home Automation and ZigBee Light Link are interoperable with ZigBee 3.0.
End devices certified to ZigBee Home Automation 1.2 and ZigBee Light Link 1.0 will be forward compatible with ZigBee 3.0.
We'd still need a new stack, so it's not going to happen for some time, as that's outside of our control. We'd of course have to test things and make sure it works as intended as well if we decide to upgrade.
Also note below, in other words, there won't be any products until 2016.
The draft standard is available to members of the ZigBee Alliance today and is expected to be ratified in Q4 2015. ZigBee 3.0 demonstrations are planned for the Consumer Electronics Show in January 2015.