Yes although the DS Lite has seen no price drop, there has been price drops on the DS as a whole.
Yes, a drop on the first gen DS because the DS Lite is out.
There was no price drop on the GBA until the GBA SP came out. There was a drop on the GBA SP when the DS came out. Jumping over to Sony, there was a price drop on the original PlayStation when the PS2 came out, and a similar PS2 drop now that the PS3 is out.
A console has never been discounted until a better one was offered. Past performance does not necessarily predict future performance, but if I were betting I'd bet against a $200 list price Wii anytime in 2007.