According to Suvudu/Bantam USA blogger Shawn Speakman, Lynch's editors are expecting the completed manuscript of The Republic of Thieves to be delivered imminently, and have already set January 2011 as the provisional date for publication. Since Gollancz have the first-print rights to the series, I imagine this means that that UK publication will precede this by a couple of months or so.
The book is finished and edited. Now his editor will read it again next week, make sure it is right, and then the book will go to the production team.
So far this late-breaking news is unconfirmed by my UK sources but I'll try to get more news on this soon.