They NEED to take care of third parties.
This isn't about having power or having sales, but catering to the publishers' desires. Here's a good example of this with the PS3. Pre launch Sony had the ICE team involved during the creation of the system. The CELL and other parts of the PS3 were really complex, but these guys had a much better understanding on how to use it than everyone else. Sony thought this was a good thing, since it allowed all of their first party games to look much better than what third parties could accomplish.
As you probably know, it ended up being a horrible thing as PS3 kept getting "bad" ports. Sony changed this policy over the years and now gives third parties everything they can. It results in much better games. With PS4 this went as far as third parties even having a say with hardware development.
Nintendo needs to do the same thing moving forward. Their first party games are amazing, but they're not enough to fully support two systems. 3rd parties are crucial if they want to be in first.
Also, they need to jump on trends and not be afraid of copying others. Take their online system for example. Matching the uptime of live or psn might be hard on their first go, but there's really no reason for them to lag behind in online features as well. Trophies, cross game chat, proper accounts, etc. should all be on the wii u.