Is Politics Always a 2.5 Party System?

I know US and UK have 2 parties, maybe a 3rd front every now and then, that never manages to come into power on its own but can influence the decision of who gets power and who gets to sit in opposition.

India has been a nation of coalitions. The nation's been divided on region/language, religion, caste etc. into vote banks, and different parties catering to these different vote banks. So, you have political parties mushrooming everywhere, but even those with a few MP seats get to rock the national stage. Now, of the short-term alliances/coalitions that were being formed, India might also be zeroing in on a 2.5 party system: NDA, UPA and the 3rd Front. Does this mean that inspite of all the parties, coalition possibilities, as politics matures you converge to such a 2.5 party system? Makes sense, in a way, you have those in power, those who oppose them and can't wait to pull the seat from them, and those who can't stand either and because 'enemy's enemy is a friend', they all align in the so-called 3rd Front.