I was going to post something pulled completely from my a**, but I have to admit that I have zero idea. The Wii's sales are unprecedented (the damn thing was the first toy to be on ToysR'Us' best buy list for Christmas on two separate years, and it may end up being there for a third year in a row...) and even Nintendo has zero idea where demand ends.
The most likely place for a price drop would be in Japan, but as Nintendogs and Monster Hunter have shown this generation, a single game can give a system a new life, if it's the right game. Animal Crossing will probably make sure there's no need for a price drop there this year, and Nintendo may well have something under wraps now that'll replicate its earlier success with the DS.
In conclusion, there are just far too many unknown variables for anyone, including Nintendo, to accurately forsee when a price drop is needed.
But for the record, I say Fall '09, just to toss something in here.







