Magic 8-Ball says "Signs do not look good, but who the hell knows?".
Honestly I've been shocked by how long and how (relatively, they have had some pretty bad numbers the last few years) well Ninty has managed to limp along on thrice-recycled nostalgia with a side order of gimmick.
The big question to me is who the hell this thing is targeting. What we know of the specs so far are unimpressive at best, not even close to high-end tablets in either CPU/GPU or display. The battery life is a big and very worrisome unknown, in fact the sheer number of unknowns this close to expected launch is at best puzzling, at worst worrying. I just don't see it going over all that well in the US and even the "They're targeting the Japanese!" argument seems kind of weak to me. Last I was in Japan -- granted, it's been a year or so -- most everyone had a tablet and/or second phone (most people have these weird flip phones as their 'main' phone, but also carry an iPhone/iPad or similar for gaming and such). Are they going to replace those with a Switch? I dunno, maybe, but it doesn't seem all that likely. Then again, I don't recall seeing all that many 3DS' when I was in Japan. Oddly, what I do recall seeing a lot of were PSPs, but quite possibly that was just because I don't think I've ever seen anyone with one in the US, especially not after the Vita replaced them, so seeing them a few times in the wild really stuck out.
As an aside, I don't tend to think the "Gameboy/GBC/DS/3DS were successes so this will be" argument really holds a lot of weight. In large measure those all succeeded as much by being substantially cheaper than the then generally superior but far more expensive alternatives (Lynx, Game Gear, PSP, Vita, et al) as much as on their own respective merits (granted, I say this as someone who owned most of the aforementioned alternatives and am still salty by their respective untimely deaths). We don't know for sure what The Switch is going to cost, but it ain't gonna be cheap and it's unlikely Ninty will discontinue the 3DS just so The Switch doesn't have it to compete with.
Edit: And in this instance by 'compete' I mean somewhat indirectly. Ninty products tend to target a younger demographic, meaning that in many instances the devices are being bought by parents, grandparents, and such, often people who have little knowledge or interest in gaming. An example of this I witnessed in a Target not long after the WiiU released. A woman was talking to a clerk looking to buy a Wii for her kid. The clerk tried endlessly to get her to understand that, given the games she was mentioned that her kid wanted to play, it was the WiiU she wanted. Didn't matter. Wii was in the name, Wii was cheaper than WiiU, Wii it was. It came down to price and the device/name seeming, at least to her, "Close enough".
Now for all I know her kid threw a fit when she came home with a Wii and she returned and exchanged it for a WiiU, but I suspect a lot of Wiis were purchased instead of WiiUs based on price and similarity of name alone. When people disinterested in gaming (or, worse, people who see video games as a waste of time, bad influence, whatever) are purchasing a device for a kid there's going to be a lot of price sensitivity.
While Ninty's name and IPs certainly played a major role, I suspect the success of the Gameboy line had as much to do with it's general relative cheapness (up until the 3DS release, and remember the ocean of tears over that?) compared to the competition as anything else.
So basically what I'm saying is that if the main appeal of The Switch is portability (and I can't see what else it would be, it's going to be extremely limited as a home console) and if, as expected, it's substantially more expensive than the 3DS, I suspect that alone could be even more disastrous for its chances of long term success than the inevitable confusion in the Wii vs WiiU naming.