Registration is now open. The promotion runs from September 14th through November 14th.
The 40th tier requires having elite status on US Airways. While it’s possible to buy a 90-day trial of the lowest tier for $200 (plus 7.5% in federal taxes), the additional 10k of redeemable miles isn’t almost certainly not worth it at 2.15cpm. I currently have Star Alliance Gold via United/Continental, so the prospect of having another Star Alliance elite card isn’t especially appealing.