Well quite indeed, gameplay is the most important part of every game. But the region and world create the gameplay in Pokemon. The battle system is just something separate. That can be fun, but seeing what Route designs, City gimmicks, and Item-ridden Caves is where it's all at. Sure, anyone can create a region, as many do with fan-made games. But it's like buying a painting (er, maybe not the best comparison). Do you go with the professional masterpiece, that captivates and inspires, or do you go with the simplistic and dull cheapy thing? Disregarding wanting to support smaller artists, the rich would go with the masterpiece.
"I'm fully expecting BW2 to be a minor update to BW."
Would you bet on it (I mean literally)?