Because MS is not a crazy coy and FTM is not a super funny program (using things that it shouldn't).
In fact from our group of FTM users, we have one that reports -
"Have just installed and run FTM2014 on Windows 10 Pro Insider Preview Evaluation Copy, Build 10074. Most of the operations I tried worked perfectly, but there were two hiccups which were probably due to the incomplete nature of the operating system. This is an evaluation (beta?) copy of Win10 after all.
Fred"
I've asked him to provide info on the "hiccups". But as you have seen from others, it is already running on the beta.
And why do I have the optimistic view rather than the pessimistic view? Because I know that FTM development wouldn't want to cut it's nose off to spite it's face.
I'm sure we will enjoy a update VERY shortly after W10 is released.
Regards,
Larry
2015JN05 17:45 Sydney