The only significant trend I see in marketing for kids is the "urban" trend. Apparently there's not much to do in the 'burbs and the city looks like fun to a lot of kids.
I didn't meant that it is interesting for revealing trends in marketing necessarily, but for revealing aspects of the current state of our culture.
The "urban" trend.. that's been big since I was in junior high school. So it's a trend over 10 years old. The stability suggests more to it than just a marketing trick. Probably is that the 'burbs are boring, or that the grass is always greener.