Overkill Software has confirmed the company is collaborating with Valve with a Payday: The Heist and Left 4 Dead crossover.
Studio game director Ulf Andersson stated:
As perceptive gamers will have noticed, several hints have recently been dropped into Payday The Heist, which has led to various rumors. We are excited to be able to confirm that an in-depth collaboration between Overkill and Valve is currently in production.
We are working on a very cool blend of PAYDAY and Left 4 Dead. I am sure it is so exciting that it will have some players check into the hospital before we are done.
Syndicate developer Starbreeze had not so long ago bought Overkill. Following the purchase, a sequel to their PSN and PC title, Payday: The Heist – which sold 400,000 copies – was confirmed. They're also believed to be working with Starbreeze on Project Mercury and V13.