Good info, thanks!

Personally I'd love to see Marvel move to WDW and be modeled after the movie franchises,
if Universal has Batman and the other DC properties available. I can almost see Uni going along with it if Disney made it worth their while to switch over and if (and only if) Warner & DC gets their act together and makes the DC properties more attractive by improving the movie presence for everybody besides Batman.
The original plan was for Marvel Superhero Island to be Gotham City and Toon Lagoon to be a heavily themed Looney Tunes area. Licensing was extremely expensive when looked at against the cost of just building the expansion. A new theme park, a set of massive parking garages, CityWalk, and two hotels with plans for a third to be added a few years later. The price tag was north of $2 Billion and it was likely to come in over budget.
Think about the theming of the original Lost Continent, Seuss Landing, and the landscaping of Jurassic Park compared to Toon Lagoon and Marvel Super Hero Island. Those last two were late fill ins for what Universal really wanted to do. They also cut corners on theming, though they did invest a lot on the ride systems in each area. Spiderman was a huge cost for building and R&D. But the general theming of that area is simple comic stuff and flat surfaces. It's even less themed in Toon Lagoon.
There's been some talk inside Universal that they want to replace Toon Lagoon with something else. I know they would like to redo Marvel to DC in some strong way with better theming, redone rides, and maybe another E-ticket. Speculation on my part, but they may have a plan on the books with WB for DC and Looney Tunes. I know they talked expanded partnership of some kind when they negotiated and worked on Harry Potter. WB is also investing in these areas too because they promote their properties. So I could see them doing the same with DC and Looney Tunes - helping to design and helping to invest, getting a share of profits from the park in the process.
For those commenting on Disney and how they would have handled Harry Potter, I have a feeling that a key to them failing to acquire the rights was their unwillingness to work with WB on licensing for the film design coupled with an unwillingness to rush a building and not coming to the table with any concepts. Universal reached out to WB as a part of their bid and had a comprehensive plan about how to get it off the ground quickly through converting some of what they had. WB liked it and JK Rowling works well with WB and likes the producers very much. I think Disney would not have liked the idea of having to let WB have so much input on design and they couldn't have done it as quickly. Hogsmeade, a new E-ticket, and a retheme of existing rides allowed Universal to get it done on a quick turnaround, in time for the final film release.
I'm not sure if a Disney vision would have included the cast of the films. Universal's proposal included the quick turnaround bit and a pledge to build a whole new area within five years of completion of Stage 1. The success of the first allowed them to expand the license to Universal Hollywood and Japan.
WB has the upcoming new trilogy based inside the Potterverse that JK Rowling is scripting, so more additions may be coming in the future.
As for other things that Universal might do, I know what they've thought of in the past. When they still had the Lockheed land by the convention center they were in talks to build a third gate as a joint operation with Cedar Fair, the owners of Cedar Point and other amusement parks. More hotels were in the offing with space for a fourth park and an express shuttle between the two properties. The third park was going to be a traditional amusement park on steroids, with enhanced ride design from Universal and amusement park know how from Cedar Fair. They wanted to launch with 7-8 coasters, flume rides, a train, a new take on bumper cars, and many other things. Alas, it was not to be.