Neowin heard rumors that Windows 8's RTM build will be 8500.0.120623-1707, and that the announcement will be made around July 17-20.
Pull up a seat if you want to hear about some new information regarding the RTM of Windows 8. Wzor, who has been known to leak Windows information in the past, has just updated a post that says Windows 8 RTM build will be 8500.0.120623-1707. We should note this contradicts Win8China's claim that the final build will be in the 8600 class.
Additionally, the source states that Microsoft will make the announcement in late July and says sometime between the 17-20. We should note that two Microsoft events happen during this timeframe. First, on the 19th, Microsoft has their earnings call and also there is the MGX, which runs from July 17-20; the source specifically states that it is coming at the MGX event.