Lets just jump into this statement, shall we?
They want to be the 'hardcore' platform. To attract the hardcore audience, you need to be a PC. The gaming portion of PC's grow exponentially faster than the console market, and the hardcore audience wants hardcore games with the most polish and least ammount of load times. The mouse and keyboard combo is also considered the most accurate thing on the market because its lacks assisting software to compensate for joysticks and less-than-stellar network cards/NAT settings. I've made the argument that these are not the most accurate, but this is neither the time nor place to revive that argument - and as far as hardcore gamers go, good luck convincing them otherwise.
Now, aside from that, what do hardcore audiences want? They don't want gimmicks in their gameplay, they want streamlined, professional quality games. For multiplayer games, this is key. From single player experiences, the demand is on polish, streamlined, deep gameplay. Lets look at Nintendo's track record. Yes, they offer highly polished single player games. But they dont have any depth to them - you never have to decide a faction in Mario, or choose to sacrifice one person to save a city (or vice versa). Its simplified so adults can have fun, and kids will understand it. Lets also look at Multiplayer. Nintendo has offered us the worst multiplayer this generation. Friend-codes instead of a unified, meaningful experience makes interacting on the Wii a hastle, and generally not worth it. They have done nothing that the other consoles can do WAY better. So I doubt you'll convert the hardcore audience on that.
You shouldnt make a console with the hardcore audience in mind. If you want to go to the extreme, which the hardcore gamers are at, you will not be able to pull them away from their PC with similar tech specs to a mid-range PC and a tablet. Thats not what hardcore gamers are looking for. If you want the "casual hardcore" audiences - aka the people who play Call of Duty and every other generic FPS, then you have a battle in front of you - how can you convince these generally macho people into thinking the WiiU is badass enough for them? Can you offer a convincing multiplayer platform? The definition of hardcore is all over the place, but I can tell you that the legitimate hardcore audience tends to stick to PC's, so good luck picking up the fairly small console hardcore market.
As for the N64 having the market, that was an entirely different time. Even back then, the hardcore audiences stuck to PC gaming. Nintendo never had a hardcore audience, it had a core audience. The core of Nintendo's appeal was making games that could transcend age ranges. Most of Sonys games were designed to hit ONE demographic, and hard. Nintendo designed their games to hit all demographics with 'complexion-through-simplicity'. Ever play Pokemon? Go take a look at some of the mechanics in those games, or watch a competitive battle. If you compare its design between audiences, they play like two different games. The same goes for most games they stamp out. Zelda, Mario, Metroid (especially the 2d ones). The N64 also capitalized on the violence debate by bringing hyper violent games, like Golden Eye, Perfect Dark, and Resident Evil to their console at the time. Not only were these in high demand from teenagers, but it helped market their device - people who wanted violence also tended to like the supurb franchises available. Sony during the PS1 Era had some really nice games, but not as many standouts as Nintendo - thats why it won the console war. And getting back to my point, Nintendo didn't have the hardcore audience back then either - local multiplayer was not something people liked to hear. It was all about online shooters.
Remember, core and hardcore audiences are different. Games have become so fragmented and broad that Nintendo can't compete. The two 'hardcore' markets are already tapped, and have a very narrow focus for their demographics. Nintendo doesnt have a persona of being hardcore,and getting one would require it to get rid of its family appeal.
If you want a core audience instead of a casual audience, put the focus back into games that you used to have. The hardware SUCKED on the N64 and GameCube. However, that allowed you to focus on aspects other than the graphics - you had superb gameplay - ones that didnt rely on gimmicks. Thats what people liked. You fell on your face when you decided that you wanted to face off against Sony or Microsoft. And while the Wii worked for a while, your lack of good IP's and the mixture of the unfinished motion control is what killed your system.