How come Fedora repos include Nagios 3.5 and not 4? Version 4 seems to have been released in Oct 2013...
Why don't you use that as motivation to see what Icinga 2 has to offer. Without getting into a pissing contest about an emotional attachment to either, see what Icinga 2 has to offer as I suspect you might be pleasantly surprised with the work they have done.
jlc