USA Capital gains exemption from sale of principal residence

[Peter96001]

I am in contract for the sale of my primary residence, which I have owned and lived in for 4.5 years. I went into contract in early November, but I don't expect to close until mid January 2018. As I understand the new House and Senate bills, the residence requirement to claim the capital gains exemption has been changed from 2 out of 5 years to 5 out of 8 years. If the current bill goes into law before I close, would the new requirements apply to me even though I went into a binding contract before the bill was passed? If I am affected by the bill, what options do I have? Many thanks for any insights you might be able to provide.