If anything, the announcement makes the Wii U even more irrelevant.
Wii U was already competing with the PS3/360 since launch, and doing substantially worse I might add.
The same people picking up a PS3/360 now aren't going to switch over to a Wii U, they're going to go after the next big thing that's seen as a tangible upgrade and not some reactionary device that's trying to play catch up to both 7 year old consoles and tablets at the same time.
Don't get me wrong; Nintendo I suspect will announce some great content (which will inevitably lead to me purchasing one), but it's going to cater to the Nintendo core audience alone, and the mass public and core gamers in general will largely continue to ignore it. You're left with a market that's approximately the same size as the GameCube (perhaps only slightly larger).
There's really not much Nintendo can do at this point. They haven't created a device that's attractive to the masses. Too little, too late.
I think your argument is partially off base. While the core gamer group who are into the ps3/xbox while ignore the wii for the most part. The broader market will ignore the wiiu until nintendo releases a software title to begin capturing various broad market segments. I'm not talking about wiifit or wiisports sequels here. I'd bet we will see quite a few casual/broad focused new IP's.
The entire system is primarily designed to maximize their chances of creating gaming experiences that have a broad market appeal across multiple spectrum. They pretty much built a better wii around a very specific driving force.
This does not mean that everything the try on the wiiu is going to catch on. BUT the system is designed to maximize the opportunity and potential to create titles that do catch on. This is what we will see unfold in the next 24 months.
They still will try and appeal to their core but on the whole they are going to make multiple attempt at the broad market. Its quite smart, let me explain in purely hypothetical scenario.
Let say Nintendo creates 5 broad consumer centric IP's following the same methodology they used to create wii sports, wii fit, brain age, nintendogs, etc. The key here is they are creating 5 new games and user experinces, not sequals. To me it appears there focus will be on creating games from a structural standpoint of emotional engagement, easy & familiar accessibility wrapped up in a tactile user experience.
(this is why they are using a tablet, its familiar to most people but different enough from competitors while giving them a great canvas to create unique experience)
The time and money required to create 5 of these types of games I bet is still faster and cheaper then producing a single core gamer AAA title.
All they need is 1 of those 5 new titles to "hook" into the mainstream audience. These types of games tend generate free PR and media attention because they surprise people and have a "fad" like quality to them. Once mass media starts talking about these games the momentum builds and now those other games in the group of 5 I just mentioned start to become more popular because they to have that mass appeal.
But all they need is 1 title to penetrate the media and start making headway into the general mass market once again.
I mentioned this earlier but Nintendo is the only game company that has been able to generate broad market interest more then once and they have done it on more then 1 platform. That fact is VERY telling and important. It shows what they do is NOT a fluke.
People have tried to argue that capturing the mass market is like catching lisghtening in a bottle. Well nintendo ias a heck of track record at doing it multiple times. This indicates they have a method to the madness, a formula or sorts. While this does not guarantee they will create a mass market winner in itself it does show the odds are in their favor.
As a betting man, I'd take that bet given their track record in the wii/ds era.