I am sure there will be at least one more wave of kingdoms, don't worry! The next great set could be a medieval fair; it has to be something like that now that we have a market village, a farm, and all the castles you can think of. This would be a perfect compromise considering the many interests of AFOL's and kids alike.
Imagine a set with a jousting match, a little folk band, a couple of craftsmen and traders selling items, a whole bunch of colorful tents and an eatery;
All in all: 2 knights on horses, 1 nobleman with 2 guards, 4 merchants/craftsmen and 2 peasants to enjoy it all!
Oh dreams....