You have stated in your blog that Mistborn had three magic systems (Allomancy, Feruchemy and Hemalurgy) and also that The Way of Kings will have upwards of 20. For comparison, how many magic systems would you say the Wheel of Time series has? Two (One Power and the True Power)? How do you classify other abilities (not necessarily related to the One Power or True Power) such as Dreamwalking, viewing the Pattern, Wolfbrother-hoodness, and changing 'luck' or chance? Would you classify these abilities as a magic system in and of themselves? Has your chance to see the background material Robert Jordan left changed how you view these abilities?
This kind of gets sticky, as it's all up to semantics. Really, you could say that Mistborn had a different magic system for each type of Misting. But at the same time, you could argue that something like X-Men—with huge numbers of powers—all falls under the same blanked 'magic system.' And take Hemalurgy in Mistborn 3—is it a new magic system, or just a reinterpretation of Allomancy and Feruchemy?
So what do I mean by twenty or thirty magic systems in Kings? Hard to say, as I don't want to give spoilers. I have groupings of abilities that have to deal with a certain theme. Transformation, Travel, Pressure and Gravity, that sort of thing. By one way of counting, there are thirty of these—though by another way of grouping them together, there are closer to ten.
Anyway, I'd say that the Wheel of Time has a fair number of Magic systems. The biggest one would be the One Power/True Power, which is more of a blanket "Large" magic system kind of like Allomancy being a blanket for sixteen powers—only the WoT magic system is far larger. I'd count what Perrin/Egwene do in Tel'aran'rhiod as a different magic system. What Mat does as something else, the Talents one can have with the Power something else. Though I'd group all of the Foretelling/Viewing powers into one.
Sounds like a topic for a paper, actually. Any of you academics out there feel like writing one?
Let's just say that The Wheel of Time has a smaller number of larger magic systems, and I tend to use a larger number of smaller magic systems. Confusing enough? ;)