So to help provide more timeline data...
Turned in Car on 12/21 at 1:30 PM ET
Received Buyback Receipt while sitting at the dealer
Chase Email on 12/22 at 8:30 PM ET
Money in account the next day.
In perusing the forums, it appears that most people are getting their Chase emails right around 8:30 PM ET (*but* adjust for your timezone - so 5:30 PT, 6:30 MT, 7:30 CT).
Since I had a midweek buyback, that meant the next business day was the next day.
Obviously, YMMV, but right as I was about to panic about not getting the email, it dawned on me to check the timezones of previous posters. And sure enough, all of them seemed to come, after adjusting for timezone, around 8:30 ET. Then the clock hit 8:30 and *boom* Chase email.
I'm all done - finished up the deal on a 17 Highlander Limited today. Will miss the Jetta. Wife already hates the Mazda 3 rental we're in until pickup from our Toyota dealer next week... "the acceleration is all wrong!"