According to Warren Kinsella, the Liberals no longer have a choice of who will be their leader in the next election, whether it is declared this month or in two years. Yes some Liberals might be wishing for a new leader, but if they attempt to replace Iggy before an election, then Harper can declare a snap election and catch the party with its pants down (like what Martin did to Harper in 2004). The message to Liberals, whether you like Iggy or not, you are stuck with him for at least one election. The sooner the election, the sooner your leader can be replaced.
Recent Liberal strategy is that they announce their intention to vote against confidence matters really early before the NDP has a chance to; then if there is an election they blame the NDP for causing it and if they support the government Liberals hammer them for propping up Harper. By withdrawing their support early, before they even know what is in the budget, this then allows them to attack either decision the NDP makes without any personal responsibility for withdrawing support...in theory. Too clever by half if you ask me; because the last time the Liberals demanded an election and the Dippers supported the government, NDP support shot up in the polls. The "you propped up Harper" attack only resonates further down the left hand side of the political spectrum. That strategy does not appeal to the center.
By trying to outflank the NDP on the left, Iggy is repeating the mistake of Stephane Dion. Elections are won in the center, not the left.