AP has broken what the big announcement later today is. Per wwltv.com:

The New Orleans Saints have agreed to a lease extension that will keep the NFL team playing home games in an improved Louisiana Superdome through the 2025 season.

An announcement by Saints owner Tom Benson and Louisiana Gov. Bobby Jindal has been scheduled for 10 a.m. Thursday at the Superdome.

A person with direct knowledge of lease negotiations confirmed to The Associated Press that a general agreement has been reached and was expected to be signed later in the week after final details have been worked out. The person spoke on condition of anonymity because the team and governor had yet to make the announcement.