As is tradition for Apple, the 22nd is a Tuesday. AllThingsD says that the event will be invitation-only, as is customary for Apple; and, the focus of the event will be on the 5th generation full size iPad as well as the second generation iPad mini. But, Apple's upcoming MacOS update, Mavericks, should also get some time, as will the new Mac Pro (though we were hoping to see a MacBook Pro update).
Also as is tradition, the new iPad is expected to be thinner and lighter, and it is expected to be overall smaller because of reduced bezels. The device is expected to be fitted with Apple's new A7 processor. The second generation iPad mini is expected to get the same treatment, along with a new "retina" display (although what that actually means is up for debate). There have been rumors putting the new fingerprint scanner on both devices, but nothing has been confirmed on that yet.
If the announcement is October 22nd, that puts the likely release date for the new tablets around the end of this month or the first week in November. But, there have been consistent rumors of big supply problems with the iPad mini, so stock could be very limited to start.