Release Candidate 2 could very well be the final beta stage of the Windows XP Service Pack 3.
At least this is what Microsoft is indicating. However, there is no official confirmation at this point in time of the fact that XP SP2 RC2 is indeed the last pit stop of the service pack ahead of RTM. The indication came from a member of the Internet Explorer team, working on the development of IE8. Microsoft released Internet Explorer 8 beta 1 the past week at MIX08, and offered various versions of the browser tailored to specific versions of Windows from Vista gold to Vista SP1 RTM, XP and Windows Server 2008.
Microsoft has already confirmed in an email to Softpedia that IE8 will be able to run on Windows XP SP3 once the third and final service pack for XP is released. At that time, I tested IE8 Beta 1 on Windows XP SP3 RC2 build 3311 and found that the browser installed and run with no problems. Jane Maliouta, the program manager for IE8 Deployment and Management, revealed that IE8 Beta 1 does support "Windows XP SP3 (RC2 candidate - Build 3311 or higher)."
But at the same time, Maliouta stated: "IE8 is not supported on pre-release versions of Vista SP1 and XP SP3. When installing on earlier builds of Vista SP1, IE8 just won’t install and you will see this error "The installation does not support your operating system’s current Service Pack version." When installing on earlier builds of XP SP3, the wizard will proceed but your system will be missing KB946501 which is required for IE8, and hence, your installation will be terminated." (emphasis added)
Now, if IE8 Beta 1 does not support pre-release versions of XP SP3, then why does it support Windows XP SP3 (RC2 candidate - Build 3311 or higher), which is essentially a pre-release version of XP SP3? Yes, I know that the repetitions are quite unpleasant, but they are meant to emphasize the fact that XP SP3 RC2 might be one and the same with XP SP3 RTM, or very close. Much in the same manner as Windows Vista SP1 RC Refresh 2 was in fact Vista SP1 RTM. But as I've already said, there's no official word from Microsoft to confirm this.