NXT was way up because of the cross overs with Raw and Smackdown and the implication Raw/SD guys would pop into NXT. #brandsupremacysynergy
I would imagine it to be back down to whatever it was once the Survivor Series stuff is over. Dynamite will probably stay around 700-800k for a while, wouldn't expect them to go much lower but also wouldn't expect them to hit 1M again outside of a major signing or crazy mainstream promotional tactic. NXT started at around 1.3M viewers as well, then was doing what AEW has done for weeks until AEW started up, so the consistent weekly audience seems to be around 1.5m for both shows. NXT I think is going to be more apt to have big swings in general due to Raw/Smackdown promotion/interactions.
NXT is definitely a better wrestling show, but AEW still has freshness, underexposed talents (although they're doing a good job of already running some of those guys into the ground like Sammy fucking Guevara), and energy that can only come from bigger crowds. I'd really like to see NXT start touring at least a couple of shows a month next year to capture some of that energy that Full Sail with like 800 people can never capture.