I'm not understanding the premise. Which is more likely to have total market dominance?
If only one, currently, it would be Nintendo.
Realistically, it could be anyone of the big 3 if they're having a good generation. But no matter how dominant Sony or Microsoft become, Nintendo will always have the ability to carve itself a profitable niche in the gaming market simply due to its software content. Mario, Zelda, Pokemon, Metroid, Kirby, Donkey Kong and lesser others will always have a decent few million fans keeping the company afloat, so long as Miyamoto remains alive and depending on how well he's taught his colleagues.