I do not think the regional parties on their own will form the government at the centre. This is because the regional parties are also opposed to each other e.g. SP is opposed to BSP, DMK is opposed to AIDMK, Trinamul Congress is not likely to go along with a combination where the Left parties have a say and so on.
If Congress or BJP, along with their well known allies are not able to form a govt., the regional parties will join or extend outside support to one of them e.g. Congress led alliance or BJP led alliance and try to extract their pound of flesh and in such a scenario, we will be back to square one.
If by fluke for which chances are remote, form a govt at the centre, as usual, it will not last long.
Your vote on this answer has already been received
In a" MULTI-PARTY-IDIOTIC-DEMOCRACY " none to enjoy majority and coalition would be a M U S T.
Some LEVEL PLAYERS, may dictate the terms, if the number of MPs are more at their hands.
Pseudo-Democracy / Idiotic-Democracy would definitely prevail.