NMB48 has just announced the release their 4th single on May 9th, 2012. No further details about this single are out yet.
The new single, still untitled, will come in the usual TYPE A, B, C and Theater version. Reservations for the Theatre version on Chara-ani will start on March 19th
As we reported earlier, NMB48 already has their live tour Osaka Juuban Shoubu on April and May, as well as the start of three new theatre shows on schedule. On top of that there is now the new 4th single. It's going to be a busy spring for the girls.
source: 1, 2