I feel like 80% of the comments on HHN's social media latest pic advertisement are all request for Stranger Things S4 and specifically with the new villain Vecna.
I know it's not well-speculated at this point, but if Universal were able to sneak it in, it'd be a huge hit at the event. If not this year, the demand makes me think it'll just haaaave to come next year (but then again, I've thought that about It, Conjuring, etc. etc...)