There is no doubt that Nintendo's always looking for the next big thing...but I don't know that any of what's currently rumoured has truth to it. But one way or another, I'm sure we'll be speculating a lot in the next little while...some of my most exciting times as a Nintendo fan and Internet user is anticipating and reading about all the GameCube and Wii news over a year before they came out, and by the usual timeline, it is about time for the next Nintendo console.
I recall hearing that Nintendo was, at least a year or two or so ago, researching the production of HVDs (holographic versatile discs) that hold a terabyte or more - which holds considerably more than a Blu-Ray. It would be cool if they could come up with their own proprietary format that had more capacity than industry standards (unlike the GameCube discs which had a third of the capacity of already-common single-layer DVDs). Having more capacity or power or speed has never been a determining factor in the console wars - in fact, in most generations of game consoles, the "weakest" in processing power ends up selling the most or being the "winner" (NES, PSX, PS2, Wii - and the Super NES, too, if you consider the Genesis's add-ons) - but it would be nice if there was one less thing to bash Nintendo about, and one less thing for developers to feel restricted by. But in any case, I do believe it will be comparable to the Xbox 360 or PS3 or even more powerful - has the "weakest" console ever had less processing power than the most powerful one from the previous generation? The way technology advances, it really shouldn't be that hard to at least catch up to five-year-old technology and to do so inexpensively.
I had a paragraph here about my disliking of the term "hardcore" and how I believe the definition is wrong - but regardless of what I think, I guess there is a user base who don't revere Mario, Zelda, and Metroid games with the same intensity as they might have in the past. (It doesn't help that Metroid: Other M doesn't quite compare to Super Metroid...) I don't know what the rumours of Nintendo courting Rockstar Games might mean. Getting Capcom to make some exclusive Resident Evil games didn't change the image of the GameCube much, so unless Rockstar Games were to become a Nintendo second-party, or at least definitely exclusive, anything they make will just be another GTA: Chinatown Wars on the DS - critically acclaimed but not a killer app for a new crowd.