Disney did not respond to Potter right away. New Fantasy Land was not their response to Potter. You don't know the process of how things get announced for D23.
I know there has been rumors for WDW before Universal announced that they are going to have a August 1st announcement according to the true insiders on this forum aka not me. The rumors the real insiders in Question are Brazil Pavilion, UK Ride, and "Black Box interchangeable ride". Everything pinpoints to Disney giving more details on their Epcot redo. All these rumors are not a response to Universal's new park because they rumors exist way before Universal announced the date for the August 1st announcement.
I think is too late for doing a response to Universal at D23. What you get out of D23 is stuff that they already planned for over a month. What gets announced at D23 is a process that even can take the last second like it did for the 2017 D23 that saw the cut of some announcements.
If Disney gets a announces new stuff after D23, it is more possible that would be Disney's response to Universal's new park. The other thing right now is we don't have date Universal is going to open that park. If that park opens in 2023 to 2025 time frame, Disney can wait after D23 to announcement something to steal the spotlight from the 5th park. The question with the park first opens depends on the Kirkman Road extension.