I think the thing to realize here is: we are only human and
volunteers, so don't expect miracles. ;)
I would say the progression should be something like:
* Keep maintaining the major version until you no longer are able to
backport or fix issues or security. In that case, move to...
* Look at seeing if there is some way you can do the major version
upgrade in a way that works with rpm and is seemless for the end
user. Discuss on this list and see if you can come up with
something. If you can, make a lot of noise and announce and then do
the upgrade.
* If you can't do a seemless upgrade, you move on to parallel installs
like we are doing with mediawiki. Announce and try and get people to
realize the flow and that they need to upgrade.
* Finally, if there's just no way, retire the package and let everyone
know it's not possible to maintain.
At almost every step I think it's good to communicate to the list and
see if others have some way forward and also to let users who search
for info find out about your package.
So, I don't think there's any hard and fast rules that can never be
broken, but a progression where we try hard to avoid the next step.
Just my 2 cents.
kevin