Maybe I'm a miserly old killjoy, but I really don't see how this is going to turn around Nintendo's current financial situation. The Wii-U life cycle was an unmitigated disaster for Nintendo, regardless of how good the hardware or software for it is (full disclosure: I haven't owned a Nintendo console since the Gamecube). I kind of see the Switch continuing that same trend.
Zelda: Breath of the Wild will probably be a really good game. No doubt about that. What I would think would be concerning to fans is the fact that the launch lineup is really slim (at least from what is known right now). $300 is also more expensive than a lot of people were expecting this thing to be, and it doesn't come bundled with a game either, so the real cost is something more like $360 or so. They'll also start charging for multiplayer now, from what I have heard.
There is a lot we don't know yet, like how good the mobile experience will be versus the in-home experience. I really hope the console is good; Nintendo could use a turn-around. I'm a bit pessimistic about it though, sad to say.