`
If P = NP is proven and generally believed by 12/31/10, then Ron will pay me
$50. If P ≠ NP is proven and generally believed by 12/31/10, then I
must pay him $10. Under any other circumstances, no money changes hands.
`

**Update (again)**: we have renewed our bet (again):

`
If P = NP is proven and generally believed by 12/31/20, then Ron must pay
Kevin $50. If P not = NP is proven and generally believed by 12/31/20, then
Kevin must pay Ron $10. Under any other circumstances, no money changes
hands.
`

Admittedly the stakes are not high, but are there any other takers?