If Disney starts mixing other characters in with The Avengers, they too will be covered by the Orlando contract. That also hurts Disney a bit.
It's this kind of speculation I always take issue with when this topic comes up, because it's clearly not that cut and dry.
Disney clearly feels they have the wiggle room to use characters that aren't flagship Avengers. We've seen the likes of the Guardians and Dr. Strange show up in the parks. And lest anyone forget, Big Hero 6 is based on a Marvel comic also, and you can still hug Baymax on a daily basis at Hollywood Studios (but he tends to slip people's minds because Big Hero 6 was animated)
Funnily enough, two Big Hero 6 members from the comics, Sunfire and the Silver Samurai did NOT appear in the movie, because those two characters are commonly associated with the X-Men, and I believe Disney couldn't legally use them due to Fox's X-Men movie rights. Despite the fact they were Big Hero 6 characters, they were also X-Men characters... and that took them out of the movie, as is my understanding
See, I don't claim I know more about this contract than anyone else, but I do think I question the finer points of it than some often do. I come at this not only as a huge fan of the Universal and Disney parks, but as a huge fan of Marvel comics. I feel I often frequent boards where one or the other exist, but not so often both. Most comic fans care more about the movie rights, and couldn't give a fig what's going on in themeparks. Most themepark fans only know the broad strokes they see in the movies, and don't know the 50+ year history most of these characters have in comics. And as a fan of both, what a lot of theme park fans don't seem to understand (in my observation) is... Marvel has ALREADY mixed ALL their characters together. In a hundred ways too numerous for me to memorize or list. Making the whole comic universe a huge blur of a grey area.
The marvel comic book universe, is very much ONE universe (or more correctly, one multiverse, but that's a level of comic-nerd nitpicking I won't bore you with). These characters all interact with one another ALREADY. They all appear in eachother's books far more often than they do in eachother's movies.
All these characters can and do already mix with one another in the pages of comic books. Spider-Man, Wolverine, Dr. Strange, Luke Cage, Rogue and 100 other characters NOT in the movie Avengers lineup have all been Avengers in comic books. On the flipside of that coin, your average movie goer doesn't know it, but Iron Man (the Avenger), Kitty Pryde (the X-Man) and The Thing (of the Fantastic Four) have ALL been members of the Guardians of the Galaxy. That is to say, the comic book Guardians of the Galaxy. Wolverine, Storm, Spider-Man and Hulk have been part of the Fantastic Four at points in the past. Scarlet Witch & Quicksilver have played strong roles in both X-Men and Avengers lore (which is a grey area we've seen make its way to Fox's X-Men Movies vs. Disney's Avengers Movies as well.)
Dr. Strange and Star-Lord will clearly be appearing in future Avengers movies, but will that make them Avengers? I dunno. But I bet Disney's lawyers are trying to wrap their head around it.
The Guardians newest movie member, Mantis, has actually also been an Avenger in the comics, come to think of it.
So anyway, having a character mix into one franchise or another clearly does NOT automatically grandfather that character into the contract... I highly doubt that Iron Man is covered by the Guardians of the Galaxy character family. Mantis may or may not be covered by the Avengers character family. Ultimately... As is often said in these discussions "It's a grey area" ... I think a lot of it is based in public perception. The general public thinks of Iron Man as an Avenger. Rogue as an X-Man. Thing as Fantastic Four. And now Mantis as a Guardian. So while Disney/Universal
could argue that one or more of these characters should/shouldn't be covered... it would be an uphill legal climb. And probably not worth starting the battle with the other company.
All that said, Disney is obviously testing the boundries of what Universal can and can't stop them from doing... and I think it's obvious to all of us that they're doing it with characters that aren't commonly perceived by the public as mainstream Avengers/X-Men/Marvel Universe heroes. Dr. Strange clearly stood in Hollywood Studios, despite the fact he WAS an Avenger and Universal's contract covers Avengers.
I just don't think we know enough to say things like, "Well if Star-Lord is in the next Avengers movie, then Disney can't use him." ... it's obviously not that simple. I don't pretend to know the details of the contract... but... grey grey grey... is what it seems to me.
It doesn't surprise me that Disney is selectively choosing which characters they bring into the parks and IF they open a ride in Orlando, it won't surprise me if it's Guardians. I will be EXTREMELY curious to see if Mantis makes an appearance in said ride.
The future will be lots of one company pushing, and seeing if the other is willing to push back, is my guess.
I personally wish they'd just have a sit-down and see if they could come to terms on both using the characters in a way that mutually benefits both sides (much the way Disney did with Sony over Spider-Man's movie rights)... BUT... that seems unlikely.