Officially, I don't know. Supposedly there's a rom available through kies mini, but I don't think it's true. But they are working on a GB 2.3.4 rom for this phone as we speak, there's been several rom leaks for the past weeks...
First it was 2.3.3 KF1, KF2 then 2.3.4 KG1, KG4, KG6 and now KH1...