Yes, that’s right. If you have an AirPort Extreme 802.11n and want to use Time Machine, it looks like you now can.
I have successfully backed up my 12-inch PowerBook G4 over Wi-Fi to my AirPort Disk… and then restored the entire backup via Wi-Fi from my AirPort Disk. It took an excruciatingly long time to do, but it worked without a problem.
So, bottom line, if you want to use AirPort Disk as a Time Machine backup, make sure you’re running firmware 7.3.2 on the base station, and make sure your Mac is running 10.5.4 or later.