From the WIzards of the Coast Webstie:
"We have made the decision to depart from prepainted plastic miniatures sets. Lords of Madness stands as the final release under that model. We will continue to release special collector’s sets (such as the Beholder Collector’s Set we released last fall), illness as well as make use of plastic figures in other product offerings. Check out the Wrath of Ashardalon board game next month for the latest example of this. Moving forward, we will continue to explore more options for players to represent characters and monsters on the tabletop, including Monster Vault and other D&D products that feature monster and character tokens."