Sad news, friends.
According to Snakas, the latest issue of Kero Kero Ace in Japan reports that Transformers United as a series will end in March, with Wave 4 and the E-Hobby Exclusive three-packs. UN-22, Laser Optimus Prime, will be the final release in the line.
There is currently no word on what Takara-Tomy will be releasing in April, but May will see the Japanese launch of the Transformers Dark of the Moon line, which by all indications will feature some alternate decos and different accessories than its US version.
http://www.tfw2005.com/transformers-news/japanese-transformers-40/transformers-united-ends-with-wave-4-171570/