With out much though, I got some old gedcom that would not open in FTM 2012. I downloaded FTM 2005 and ran it. Since you asked the question I realized it was on Windows 8.1. Since I was able to convert the gedcom to a newer version, and I did it in FTM 2005 on Window 8.1, the answer to you question is yes.
I suspect that if you were fully using FTM 2005 on Windows 8.1, ie internet access, local area networks, etc. you may have trouble, BUT you are only using the open and save functions, a minor part of FTM.
I second the motion to wait until FTM 2016 comes out probably in September or October.