Diablo III, but there are also several people looking forward to Torchlight II, the followup to the hugely successful spiritual sequel to Diablo. A recent interview with Max Schaefer, co-founder and CEO of Runic Games, discusses the development of the sequel including some of the contrasting points between it and Diablo III -- including the lack of any sort of virtual item shop. As Schaefer puts it, the team wants to put together a good game that stands on its own, and if it's successful the developers will look in the direction of an expansion rather than a straightforward shop.
Schaefer also discusses a potential MMO coming out of the studio, something that's long been among the studio's plans -- one of the big reasons that Runic partnered with Perfect World Entertainment was due to its expertise with running an MMO. He claims that it's definitely still on the table, but it would be a big change for the studio, since the company has focused on staying small and launching an MMO is a very long-term commitment. Somewhat sad news for those hoping that Torchlight II's launch would spearhead MMO development directly, but the possibility certainly remains.