Nope, To make Modi the PM of India, BJP doesn't need 270+ seats, ofcourse to need simple majority a party or an alliance needs 272 in the lower house of the Parliament but we are forgetting that Post - 1990 is the era of coalition politics where 200 is the new 272. If BJP touches the mark of 200 come 2014, the secularist ideology goes for a toss & BJP can make anyone the PM of India it wishes. Many Political parties which have supported BJP in the past will be more than willing to support BJP again, since in the era of Coalitions, one party doesn't necessarily needs a simple majority anymore, politicians just have to judge the flow of the wind is in what direction, & it is of no doubt whatsoever that if BJP will win 200+ seats, it will only be because of people's assumption that Modi will be made the PM, now no party can go against the wishes of the people of India.
If we look at the trends which the latest India Today survey showed, NDA (BJP, JDU, SS, AD) as of now (when they haven't disclosed there leader) is winning 208 seats in which BJP will get around 160+ seats, this figure is only rising from the 2010 surveys of IT, so even if the status quo is maintained (i.e. no disclosure of leader & no change in NDA) than also NDA can end up with 225+ seats ( i m even assuming of a simple majority for NDA given that analyzing last few state elections have shown that the Party/alliance seen close to getting a majority (in surveys) have been given a thumping victory by the people, eg. SP in UP, BJP in Gujarat, etc.).
Now if BJP declares Modi as the PM candidate & NDA becomes NDA - JDU, but than BJP tally will only increase (maybe cross magic figure of 200) even in Bihar, as some surveys suggests that Modi is equally favored in Bihar as in other parts of India, so it will be loss for JDU & not BJP.
+ there is every possibility of MNS & AIADMK joining NDA before elections.
Given that BJP will rise as the largest party after elections, no other party can ignore it & they will be forced to form a coalition. As it is, in Politics it's not about IDEOLOGY but about POWER.