Huh? The weaker the Yen, the more profits Sony / Nintendo make overseas...which is the bulk of their sales.
That means they make more money.
But the yen isn't weak. It's still very strong and far too strong for their overseas business. 87 yen to 1 dollar is better than the 75-80~ it's been floating around for a year or two, but it was 130 yen to 1 dollar at the start of the generation.
Edit: I own the 5 millionith post on VgChartz. Huzzah!