Quote: "You need to stick with the new version of Xcode in order to be able to communicate with the newer iOS devices."
Not necessarily. I have iOS 5.0.1 on all of my devices but am still using and old version of Xcode 3 on Snow Leopard for a lot of development.
If you have a version of iOS that is greater than the SDK of Xcode and it won't let you build and test on the device, you should be able to go into Organizer and click 'Connect' for your device (it will say it has an unknown version installed). In a few minutes it should be up and running (the base SDK will only be the max supported by your installed version of Xcode, of course).