I do buy systems when they're new-ish, but I love when they begin to die off because I can really stock up on games for dirt cheap.
GameCube, though - as people have pointed out - is a pain to collect for now. It's hard to find used games, and the ones that are available tend to be overpriced. It's definitely because of the Wii. Even though I own a Cube, buying a Wii absolutely rekindled my interest in the earlier system. With that said, I managed to grab Geist, XGRA, and Odama for $10 each recently. Those may not be fantastic prices, but they're still pretty good (for Canada anyway).
BTW, for the people waiting for the PS2 to drop from $120 to $99, just buy it already! Do you really think it was worth not having a system for a year or more just so you could save twenty bucks? Come on now!