The current RPM repository metadata format has existed since Fedora Core 2 in 2004. The build system infrastructure changed to Koji in 2007[1]. The development model has changed exactly once when Fedora switched from CVS to Git in 2009[2].
There have been no significant changes to Fedora packaging model until three years ago, when Modularity was introduced[3] and Pagure was deployed to ease contributions and support building modules[4]. And the modularity concept is primarily used for alternate software streams in Fedora, so the vast majority of Fedora packages don't use this feature.