[...]Well, as someone that maintains rpm packages in different repositories for some years now I tend to doubt that -- the interdependencies of FLOSS software are way to complex: lot of stuff further is moving in parallel forward quickly all the time and makes it ever more complicated.
The look into the crystal ball
The OBS could become a central place for distributing software in
the FLOSS world: every software project could create the necessary
binaries there for all bigger distributions. [...]
Sure, for a pure apps that does not provide libs to be used by other software I suppose it will work in a acceptable way (well, as long as the distribution they were build against don't do major updates to library packages without providing compat packages. Which is the case in Fedora; see recent libupnp update -- soname was bumped in new version but no compat package in sight afaics).
It should even work to get one or two apps with libs from the OBS add-on repo for Fedora to have them always in their latest and greatest version.But I tend to think the more uncoordinated repos you mix the more problems users will run into.
Heck, even within Fedora we run into broken dependency's in our own repos often. Then there are the inter-repo problems into which users run now and then when they try to mix the three big 3rd party repos for Fedora. Now just imagine what happens if five uncoordinated mini-repos from the OBS with libfoo, libbar, foobar, baz and barbaz come into the mix... Sounds like major trouble to me.
Well, time will tell -- maybe I'm painting it way to black here. Or tools (RPM, yum, ...) will get better.
The imho real solution for the Fedora project would be to have special experimental repos for special things that are not yet ready for rawhide or stable. KDE4 would be a good candidate for such a repo atm; kernel-vanilla as well. Maybe it would even be the right place for kernel module packages.