The mobile phone market is one of the largest in existence. One mobile phone contract exists for almost every person on the planet (the fact that some don't have a phone is compensated by those that have multiple SIMs/contracts). Half of those contracts already run on smartphones, most of the rest are expected to follow within five years. One would think there is more than enough room for all the competitors.
Unfortunately, it appears consumers want nothing of it. 75% of all the profits are made by Apple. Samsung takes most of what is left, while the rest fight for scraps. Companies like HTC and Nokia can barely break even. I don't know how BB is doing, but I hear they aren't fairing much better.
Theoretically, I too support the notion of "the more the merrier", but due to the way the market currently behaves, I must assume smartphone enthusiasts are the only ones who care. Everyone else appears fine with two choices, and I think we can consider ourselves lucky if a third viable option emerges. I doubt a fourth player can cut off a sizable enough chunk of the profits, as to allow enough reinvestment into R&D to remain competitive over the long term.
I too hope BB succeeds, but if we can only have three, then I would prefer WP.