Nintendo needs to strengthen their third-party support, because Sony and Microsoft are finding ways to offer consumers so much more than just a game console, while still maintaining the game console at the core.
As for the Sony studios being closed? Zipper Interactive developed 3 games that sold terribly (Socom 4, Unit 13) or didn't perform well enough to cover the cost of running consistent online servers (MAG).
And BigBig Studios wasted time and didn't get anything going on their own after Sony bought them out. Look at the other company that was bought at the same time BigBig Studios was (Evolution Studios) and you see that Sony was a little too optimistic with BBS. Zipper just fell apart, I'm not sure what happened with them, but they killed themselves. The fact is though is Sony isn't aggressively going after third-party exclusives as much anymore, because they are spending that money on internal investments. Zipper and BigBig were shut down, but Sony still has the most first-party studios.
If Nintendo is not careful they will not perform like they did with the Wii. Any negative press will dampen the Wii "brand". Just look at PlayStation. It use to sell millions and millions on just the name. Then Sony closed their doors and stopped being developer/publisher friendly like they were for the PS1/PS2. As a result the third-party devs decided that if they were going to have any shot of staying around, they had to get their games in front of as many gamers as they could and the era of console exclusives started coming to an end.