Any government that is dependent on the three wingnut Independents is on very shaky grounds. Abbott's best bet would be another election.
If Oakshot defects to the Coalition, there will have to be another election of the lower house.
If two independants defect at the one time, Abbott becomes Prims Minister, then his best bet would be to have a double dissolution if the occassion arises and hopefully rid the Senate of the Greens or he could call an election of the lower house to gain a larger majority. His problem will be the Senate where the Greens will hold the balance of power from July 1 2011.