Here's what I think is going to realistically happen.
Warner Bros is going to continue to aggressively expanding Horror Made in Hollywood. If it does well this year (and I suspect it will), that'll close the door on Universal obtaining any headliner properties (Exorcist, Shining, Conjuring, It, etc.). I don't think this necessarily precludes Freddy or Jason, as those characters span a pantheon of films owned by different studios; work-arounds definitely exist and have been used before. Those restrictions will inevitably extend to the Orlando event.
Meanwhile, it looks like Fox><Disney is going to happen. Disney is likely going to slam the brakes on licensing out any major FOX horror properties, in most circumstances. Why? Because there's now actual competitive reasons to do so: Horror Nights Orlando is no longer a backwater local hangout the way it was in the 2000s. It's now a literal vacation driver; look no further than the way Universal aggressively markets HHN throughout late Spring and Summer, with an emphasis on larger vacations that include Horror Nights. Those vacations are a threat to Walt Disney World - not Horror Nights itself. So Disney/Fox has a reason to withhold the properties; diminish the value of Horror Nights, diminish the value of those vacations.
So where does that leave us? Horror Nights will have to adapt to survive. They obviously have their in-house properties via Blumhouse and other production companies. They have their extensive back catalogue of horror films to pull from (Classic Monsters, The Thing, etc). And then there's the unaffiliated companies left - Paramount, Lionsgate, Netflix, Hulu, MGM, Amazon - that aren't participating in the haunt game. Universal will need to rely on those outlets more than ever to fill the roster. It's also possible they can procure "cult" releases that aren't considered vacation drivers (i.e., not Halloween 2018) - think more in the vein of Trick r Treat - from the Fox/Warner Bros industry titans.
For Orlando, this really isn't a big deal at all. It means we get years like the forthcoming one: a big ticket property to sell to the GP, a handful of smaller but exciting properties (including a piece of marketing synergy or two), and a wider lineup of original mazes.
The implications are far greater in Hollywood, which historically has far less experience in executing original mazes. Ironically, the ones they do attempt (La Llorona & El Cucuy) have been generally well-received, with the former receiving massive acclaim. If Murdy sticks around, I feel we'll see more "rock star" or celebrity-endorsed mazes to "original" concepts (Black Sabbath, Alice Cooper, Clowns w/ Slash, etc.). If he doesn't, we'll see a more pronounced shift into "original" but super-marketable original ideas (emphasis on clowns or cultural legends). That'll help fill the slate when there aren't enough legitimate horror properties left to work with (and yes, they're eating through them faster than the industry can supply new possibilities).
So, final conclusion if you don't want to read the above: Orlando is safe, this probably means more originals and cult properties. Hollywood will have to adapt if it's going to survive, but it's very possible for it to do so.