Not that I'd know, but here are some options for what might happen.
1. Rudd does the sums and works out that he doesn't have the numbers. So he quits politics explaining that he can't work under JG. We have an election and Tony Abbott wins.
2. Rudd does the sums and works out he does have the numbers. He challenges in an open way - not quite like JG did last time. He wins and we have a fresh start before the election and labor has a chance of winning.
3. Gillard does her sums and works out she has the numbers. She challenges him for the leadership and wins. Rudd moves to the backbench and sits and stews quietly. Things mumble along and labor goes down big time in the election.
I rather like option 2.