You could guess a couple more million still using like older core 4 and core 7 installs as those are not getting patches any more. There is software that demands core 4 to run and people will only update to minimal requirements. There is also software that demands the kernel from core 7.
Now of those 12.5 million most are on the oldest supported platform and not actively testing the latest and greatest but the active latest platform testers has grown dramaticly since core 10 started it's cycle.
Community noise from fedora is dwarfed by ubuntu. If Ubuntu came out and claimed 60 million users. I would be hard pressed to try to mount a dispute of that claim.
Fedora has been working on a more efficient patching system for couple years now and it's finally rolling it out. They'll probably be piping a few dozen less terrabytes of data this year from it. Now even if half of those users are transition phase from windows dual booting back and forth waiting out software that works like they want it under linux etc it's still impressive growth.