The idea of a coalition government is dead for the simple reason that it is not in Michael Ignatieff's political interest to enter into a coalition that would require him to share power. Although it is in his political interest not to contradict Stephen Harper's coalition fear mongering but to leave the impression he is opposed to a coalition because of it's supposed illegitimacy.
Of course, if coalitions were illegitimate the governments of most western democracies, including that of the United Kingdom that our government is modelled on, would be illegitimate.
It is clearly to the political advantage of the Liberals to reject a coalition and try to leave the impression that the only way to defeat the Harper Reformatories is to vote for the Liberals. That is not true of course. Strategically speaking the best way to defeat the Harper Reformatories is to vote for the candidate in your constituency that has the best chance of defeating the Conservative candidate.
If the Conservatives do not receive a majority, but receive another minority and face the House of Commons and attempt to govern as if they had a majority (as they have in the previous Parliament) they will face certain defeat, either on their Throne Speech or Budget, leaving the Governor General bound by precedent to ask the Leader of the Official Opposition if he believes he can form a government. Michael Ignatieff would most certainly reply yes, and as long as his government acted responsibly, presenting measures that a majority of the House of Commons could support, he would be able to govern.
The situation was different when the last coalition proposal was put together because the constitutional precedents become less clear and certain the longer a government is in power and it was deemed advisable to present the Governor General with a very clear indication that a stable government was possible because, despite Stephen Harper's irrational ravings, coalition governments are much more stable than minority governments.
So despite Stephen Harper's desperate fear mongering (over something there is no reason to fear) the Liberals will not enter into a coalition simply because it is not in their political interest to do so.