Originally Posted by ElevatorEnthusiast

It's still bookable for tonight and the message on the website says:

Effective 12:01 a.m. local time October 1, 2025, Thompson Atlanta – Buckhead will transition to a hotel brand outside of the Hyatt portfolio and is expected to honor all paid reservations. Guests with questions regarding stays at the hotel October 1 and beyond and World of Hyatt members with reservations for award nights October 1 and beyond should contact Hyatt’s Global Care Center at 1-888-848-9496 for U.S. guests or 1-402-952-1131 for guests outside the U.S. For bookings made via online travel agents or other third parties, guests may contact their booking provider for information on their policies and for assistance.

You should call Hyatt.