|Tale 2 (Chapter 45) was released recently. Man I can't wait for more (College Jun is way more likable than the high schooler Jun).
Spoiler (highlight to view)
From the looks of Tale 4 (Spanish translation), Suigintou is the next to join after Shinku. I think it's pretty cool how his older jaded self is able to attract a more mature Rozen Maiden (Compared to Hinaichigo and Suiseiseki anyways).
Though I suppose she only joined for the sake of a common enemy (Kirakishou).
Even though it is serialized monthly in a weekly magazine, there should be raws for up to tale 6 now (At least).