I know its a cop-out answer, but it is the truth. It depends on matchups (and who is healthy).
If everyone is healthy, and they are facing the Heat, who will likely have Lebron playing PF down the stretch, then I definitely think Green will be in the closing lineup. If they are facing the Lakers, who are closing with Howard and Gasol, Green will not be out there.
I agree. And Jeff Green playing 4 against Lebron, or Durant should both teams make it that far, means he won't be playing out of position, and thus overpaid as a mediocre 4. Those will obviously be difficult matchups for him (or any player ever), but it's better to have Green in that slot than a traditional PF.
Of course, as more teams copy the Lebron and Durant model and have larger wing players move to the 4, and essentially play with three wings, Green will probably see more time at the 4 too. But then he won't be out of position, he'll just be playing a newly defined position.