Demos tell you hi
All demos have done for me in the past is get me pumped for something ballin' before crushing my dreams with the final product. Really, I'm good with waiting for the actual game before determining whether or not its a real gem or a neatly wrapped piece of !@#$%, ala Fable III.
But yeah, Nintendo. I'll probably end up buying this simply because I'm still a Nintendo fanboy at heart.
Nintendo also agree with demo's being bad in that way (or rather the opposite of wanting you to play the final experience, not a bit of it) and haven't liked demo's for as long as I know.
I doubt they'd suddenly jump on the band wagon over their beliefs.
I of course have no idea how the next gen will be, but if there is only 8 gigs of space (I do like that it's flash and fast tight butthole though) and more is needed because of Nintendo suddenly going into tons of downloadable content or whatever, then cloud storage may be a possibility. Goes in line with the rumoured name of "Stream" as well.
Of course it's just speculation though