I don't think the surprise is Mummy enhancements--if only because I think he would've talked about it by now if he had.
Unrelated to the secret project, but I wonder if we actually get both Murdy and Aiello teasing/hyping the 2026 event. This will be the first time that both coasts will be sharing the opportunity of celebrating anniversaries together following COVID causing things to be shifted in Orlando not celebrating HHN30 until 2021. I could see them both talking on a small level of their approach to what next year will be.
Especially as in the case of Hollywoods--we will be turning 20 on the public level next year. If nothing else, more in vague statements, but statements nonetheless.