A transition is needed for certain package-groups that influence a lot of other packages. Perl is a good example, because it is basicaly every in the system. So if a package like perl and perl-foo gets updated, you have a transition, that has to ensure that all packages depending on perl or a subset of it, gets built against the new version, sometimes in a certain order. So this will take some time, because all the maintainers of the dependent packages have to take action.
The problem with this is, that we base on debian unstable. Our strength in such cases is turned into a weakness. That is due to the attitude of some debian developers who do not care if unstable breaks or not. My guess is, this will take ~ another week, at least as far as it bothers us.
greetz
devil