Since my original proposal  was rejected, before there was even
single attempt to improve my draft, I am moving this topic here in hope
that somebody can build upon it:
Always consider to let a nonversioned package to follow an upstream
release versions. The other versions of package kept in Fedora for
compatibility reasons should be either prefixed by compat- prefix or
their name should be suffixed by version string.
For example, lets have in Fedora foo package of version 1.0 (foo-1.0)
while upstream releases version 2.0.
1. If you are reasonably sure that the 1.0 version of foo package will
be needed just temporary, then update the original package to
foo-2.0 and introduce compat-foo-1.0 package.
2. If there might be more then one older version of library, then
migrate the foo-1.0 to foo-2.0 and introduce the compatibility
package foo1-1.0 or optionally foo10-1.0 package (the version in
name depends on versioning scheme used by upstream).
Try to avoid foo2-2.0 package as much as possible, since it prevents
innovation and make package version irrelevant.
There was also a lot of valid feedback on FPC meeting , so I hope you
guys are going to elaborate here.