Assuming the speculation is reasonably correct, i.e a step up from current gen but not a full generation gap, I think one early key for Nintendo is how exactly 3rd party ports turn out and are positioned.
If 3rd parties literally just port over every current HD game and that is all the system gets for a year, I think Nintendo is really going to struggle in differentiating the new system from PS360. While I'm sure Nintendo thinks the ease of porting HD projects is a significant positive, there is a danger if that is all 3rd parties are providing- it could essentially permanently label the next system as part of *this* generation, and no more.
Now, if there is a mix of pure ports, upgraded ports, and some original stuff that demonstrably looks better, then I think Nintendo is in a good position.
Obviously, a killer game made by Nintendo that blows everything away would help as well.
I think Nintendo has to walk this tightrope very carefully.