Yes, I have seen that (not up-to-date) sticky post and I have searched for quite some time now for recent information about KMail 2, like "3rd Beta released today, known bugs:..., Next Beta: xy Sep.", but I couldn't find what I was looking for, not in Userbase nor on pim.kde.org nor on PlanetKDE nor in the official mailing list archives.

I'd be very thankful for that one relieving link (I'm sure there must be one?)

EDIT/KIND-OF-SOLVED: Seems like release-team is the right list to look for.
It's not perfectly what I was looking for, but I found out about the date ob Beta3.

I would like working packages for opensuse myself. I found the repo thanks to a comment on news.kde.org but but it is requiring kdebase-runtime >= 4.5.2 but I haven't heard anything about it's release. Anyone have any ideas? or should this go to an opensuse forum?