Looks like this program is continuing into 2020. Logging in shows a fresh $200 to spend in 2020.
I signed up for Amazon Prime and Costco in December. The Costco rebate processed automatically and was credited back to my account a few days later.
The Amazon Prime did not, which seems to be because Amazon charge sales tax on Prime in California (and apparently some other states) so the amount was $129 rather than the $119 Citibank were looking for. A quick call and they were able to open a claim for it, and apparently it'll be credited in the next week or so (but still against 2019's balance)