"Is it a definite that the $2700 benefit is going away after 2024 ..."
From the occupational side of the house, no. This is what they said in a letter to the unions:
"Since 2015, AT&T Medicare-eligible retirees and their Medicare-eligible dependents have been able to enroll in health care through the Aon Retiree Health Exchange (Exchange). The Exchange provides a wide selection of insured medical, pr-scrip-ion d–g, dental, and vision plans so you can elect the coverage that works best for you and your family. As part of our continued support of our retirees, we will continue to credit a Health Reimbursement Account (HRA) in 2019 for eligible participants. The HRA can be used to help pay for individual insurance coverage and eligible out-of-pocket expenses for those who enroll through the Exchange. The experience within the Exchange plans has been positive and we are able to keep your HRA crediting amounts through 2023. Beyond that, future changes in HRA crediting amounts, if any, will be based on several factors. These factors may include business conditions, government actions, marketplace changes and the general consumer inflation rate."
There has been nothing said about what may transpire after 2023 for occupational retirees.