Maybe it's just me, but I'd much rather see a common source format for packaging. That way, I could create one description of the package and could be processed into packages of whatever formats I provided enough information to support. It could even have a lint mode that would tell me that my description is adequate to generate an RPM for just about any version of Fedora, but if I wanted it to work on Ubuntu, I needed to provide a startup script in X format.
A common specification format together with a rich policy database would make it much more likely that upstream maintainers could produce reasonable seeds that distributions could use, and might help unify tool development (ah, I see you're using git to hack on your local copy of this package, and version 2.13 is in your history. I'll generate a source bundle that includes the virgin 2.13 along with all of your patches automatically.)
I suppose this could be done with a meta-source bundle that generated sources for all the different package systems and distro flavors, but it seems an unnecessary layer. Probably the best way to get started, I suppose.
The reason why I haven't taken a stab at it is because I've gone through much pain to be semi-competent at building RPMs, and I'm not anxious to go through that much pain again for a different format. (I took a brief stab at learning dpkg because I keep hearing how incredibly awesome it is, and at least from the building side, it just seems to have a different set of miseries. I don't know whether it's nicer overall or not, and I don't especially care since I don't need to know it.) I'm guessing that's a common stumbling block -- the people who know this stuff deeply enough are wedded to a particular distro, since that's *why* they know it that deeply.
One last comment -- when talking about package management, the users people are normally thinking of are the recipients of the packages or the distribution maintainers. I'm in a 3rd category: I build lots of new or slightly customized RPMs all the time, but they are for my own use and that of a small network of other people (usually the other people at my company.) If package building wasn't such a pain in the rear, there would be a lot more people like me. Currently, most people seem to compile and make install on a dozen different machines rather than fight with building a package once.