Depreciation question

  Our fiscal year runs from October through September.

I understand that the bonus depreciation is not in effect for assets placed in service after December 31, 2009.

We depreciate out federal tax book every month and are concerned that the US Congress may change this retroactively. My question is this –

If we have depreciated our federal tax book through August 2010 using non-bonus depreciation methods, and Congress passes an act declaring that assets placed in service in 2010 are eligible for the bonus depreciation,  if we associate the ‘bonus’ depreciation method with assets placed in service after December 31, 2009, and run depreciation form September 2010, will all of the depreciation for the assets placed in service during 2010 be recalculated under the bonus method?