Remember, a Bill is simply a proposal, but once Congress approves it is a Law. However, I really don't think that this part of the bill would undermine the current "First Time Homer Buyer Credit" as an enormous amount of time was spent drafting this bill and eventually having it passed in the law!
Still, it seems that you have become quite familiar on this subject and perhaps you should wait a month or so before filing your taxes. Until then, just wait it out. If you elect to choose the new proposal, clearly I would think that the offset would be receiving less in terms of the tax credit, so as a taxpayer you have to weigh out your options carefully and discuss this with your CPA or Tax Adviser.