I can't prove it with numbers, but I think that the sport of basketball is not growing in popularity anymore here in Germany. But it has become more than just a niche sport. I think it's more popular than handball or volleyball. Some TV channels broadcast matches on a regular basis, which has not always been the case.
However, the real boost happened after 1992, after the US Dream Team impressed the word at the Olympics. After that, everyone seemed to play basketball. Street tournaments were nearly everywhere and clubs rose in numbers. Cable and satellite TV showed NBA games and there was a real hype about the sport. Unfortunately, this trend did not last, even though the German national team occasionally did well. I don't know why but basketball in Germany seems to have reached a plateau. I don't think that it will ever be remotely as popular as soccer/football. I guess it's a cultural thing. Kids play soccer/football. Seems to be set in stone.
As for Schroeder, he exceeds everyone's expectations. Incredibly fast. Amazing how he takes the ball to the hoop. But he will never become a basketball legend like Nowitzki. Different players, different characters. Can't be compared. Schroeder will keep improving and if everything runs smoothly, he might even be an All-Star one day. But his jersey will never be retired.