Deep down I'm really hoping they bring a non-IP E-Ticket to Frontierland. It's worked well recently in other Disney parks (Mystic Manor at HKDL, heck even Everest), but I'm doubtful that WDW execs are willing to forgo the the IP route.
With the plethora of successful IP that Disney now has (Lucasfilm/Star Wars/Indy, Pixar, a resurgent Disney Animation Studio, tons of classic animated and live action films), I'm sure it's hard for them to watch Universal exploit so many IPs: Harry Potter, Marvel, Transformers, Simpsons, Jurassic Park, Kong, uhh... Fast and Furious (lolol).
I think Disney knows there are certain situations where an IP isn't necessary (somewhat recent history includes Everest, Soarin, Test Track 2, Mission Space), but they also know that taking advantage of a property/franchise is smart (Harry Potter single handedly put Universal back on the map, and magic wands and butterbeer sales could solve the economic problems of a small nation). Attractions like Tower of Terror, Splash Mountain, and Star Tours are wildly successful E-tickets "despite" being based on various properties.
Disney has always understood there's a need for a mix. While I can't think of anything that's a 100% perfect fit for Fontierland, Disney doesn't have a habit of using wildly inappropriate themes. I hear you screaming "BUT
OMGFROZEN," but like it or not, it's not a wildly inappropriate theme for Scandanavia (of which Norway is a part). Now, whether or not it's a fit for World Showcase can be debated, but we can do that in the proper thread, until a polar bear gets tired of standing on two legs. Monsters Inc Laugh Floor? Okay, a pretty odd fit. It's not futuristic or Sci-Fi,
but it's also not
obtrusive (Imagine if there was a Monstropolis in the middle of Tomorrowland... that's the kind of thing I'm talking about that they simply don't do).
So sometimes the attraction itself isn't ideally suited, but Disney is always respectful of the facades and outward appearance so as to prevent terribly jarring juxtapositions. To me, that's the one thing that MK has always tried to avoid, Splash Mountain not withstanding
cuz that thing be a bit out of place in Frontierland but whateva it's awesome.
My point here is that I think we need to just wait until there's something announced before we worry about whether there will be an IP in the proposed attraction or not. Disney parks are the best
theme parks in the world, and they're under much more intense scrutiny than the Universal parks down the street. Universal makes every single attraction themed to an IP, and they don't have to worry much about inappropriate themes. An attraction doesn't fit for a land? No problem. Tear down Jaws and build a new land. Don't have enough room for Harry Potter at IOA? No problem. Re-theme every single attraction and restaurant in an entire land (Merlinwood) to Harry Potter. They don't have 40+ years of history to respect. Disney can't just re-theme Frontierland to an IP that has similar architecture, because 40 years of history stands in the way. People are so much harsher on Disney's thematic choices than any other park in the world.
This is the trouble Disney has at the MK. It's a bit easier at DHS, because it's a movies-themed park. Almost anything goes (like at Universal/IOA).
But anyway, I have my doubts that Disney will use a big name IP for a potential Frontierland attraction. There really aren't too many wildly popular IPs that would make any sense. With Toy Story attractions already existing in two places (DHS, Tomorrowland), I doubt they're going to put it in Frontierland. It's just ... why? They don't need to further capitalize on Toy Story (or Pixar in general, especially with Pixarland on the way).
I don't discount, however, that they might use a lesser known IP for Frontierland, the same way they did with Splash Mountain 20+ years ago. A cartoony attraction, perhaps? It would be completely at home next to Splash, Big Thunder, and Country Bears. Maybe a Mickey Mouse (or Steamboat Willy) themed old west ride? I don't
think it'll happen, but it could, and it would be totally appropriate when looking at the tone of the surrounding attractions.