As said by some above: (And this really goes for any console)
Yes - If they want to take first place in any generation they will need Japan. They may not need to win Japan, but they will need to have a very strong showing. This means that they will also have to win the other two markets.
No - If their main concern is to beat Sony, (and I believe it is) they don't have to do well in Japan. But not doing well in Japan makes it that much harder for them to stay ahead in the World wide race. Not impossible, but very hard.







