I enjoy Wizard 101 and Pirate 101, Pirate a bit more than Wizard, and am a little disappointed in the diversity. The Spiral is set up to be this expansive sort of multiverse but all the players can be is Wizards and Pirates, that's a little limiting if you ask me. And, to top it off, there's no mechanism in place to allow the games to crossover for whatever reason. I also adore the steampunk aesthetic of both games, any further games in the worlds of the Spiral can easily keep the aesthetic and feel of it all.
I while back I came up with some game ideas to expand what the players can do and/or be. The first idea I came up with I took to calling Mechanist 101, a game where you can be different kinds of machines. Due to that game's structure being built around a type of person that makes and fixes gear, usually, I was thinking that game could focus around players actually crafting gear and items, so instead of getting the gear itself you get the plans for it and make in your workshop/lab. I actually came up with a few different types of mechanists for this game, but I won't say here for now because I'm running out of characters.
Another idea I had I took to calling Spiral Adventures, this game is a bit different and would require a few more games in the family that Wizard and Pirate are part of. Instead of making a new character you can just take an existing character from another game and go on adventures with friends that way, the idea with this game is to have one person take the Wizard they really like and another Person take the Pirate they really like, and this would work with whatever other games in the series there are, and go on adventure with all those different characters and see what kind of adventures you can have that way.
Given how popular they are, I'm sure some people would like to see a Ninja 101 game as well. That would be pretty fun, having a stealth-themed game where you start off exploring Mooshu.
Honestly, there's a lot of different ways to expand the games, but adding more games to the family would give things a bit more diversity.
Given that W101 came out during the height of Harry Potter mania and P101 around the time Jack Sparrow was box office gold, I've always thought that the next iteration we'd see from KI would be a game where your character was an enhanced meta human. Heroes 101 seemed to be the perfect idea.
Alas with the lack of updates to P101 and the decreased numbers of visible players I doubt we'll see any new MMORPGs from KI. They seem to be concentrating on apps for mobile devices.
That said, I WOULD love to see a crossover between Wizards and Pirates.