Sadly for me, I am not you, and I do use DVD studio and I had QT7 pre-installed (albeit I had to dig deep to get it out of utilities on my recent mac pro which i got about 2 years ago.
Also, sadly for me, I am not you so I still want QT7 installed because it has functionality QTX doesn’t have and works better for me than other conversion apps I have.
So, I’m still glad FCS works in Mavericks, I still want QT7 on the new mac and I have no idea if it would or wouldn’t run on the new mac because my head is devoid of that sort of information or the ability to guesstimate through technical knoweldge.