Malte,
The reason we don't support upgrades to development version is a pratical lack of resources.
The way to reduce the length of time before release of OpenACS 5.2 is to dig in, test, fix bugs, and basically make the release happen. Anyone in the community is encouraged to help out in any way they can, by testing, reporting bugs, submitting patches, cleaning up the bugtracker. Anything. If anyone would like to help, but does not know how, please post to the forums or visit us on IRC at #openacs https://openacs.org/irc/
