Fedora roadmap is now mostly synced and compatible with PHP one.
Fedora 25 was released with PHP 7.0
Fedora 26 will be released end of June with PHP 7.1
Fedora 27 will be released end of year, as PHP 7.2
I plan to submit a change proposal to have PHP 7.2 as default version in
Fedora 27 very soon.
The only risk I see is a possible schedule slip (PHP side) which will
make Fedora delivered with a RC version (but seems acceptable).
We should be able to import PHP 7.2 beta/RC during this summer, which
will give us ~4 months to fix possible breakage.
It will also helps a lot upstream developers to have this version
monitored by Koschei ASAP.
One of the big change is the removal of the mcrypt extension (I'm
fighting for years to see this disappear from package dependencies),
btw, we can provide it, if really needed, using the pecl ext.
FYI, PHP 7.2 Software Collection already available in my testing
repository, so we can start using it for tests (I already start to use
this version for running library test suite, when possible).