Here at MIX, the RC of WCF RIA Services has been announced.
You can find out more about updates in the RC to ease deployment of RIA Services applications here.
And Brad Abrams’ announcement of the availability of WCF RIA Services RC is here.
UPDATE: Just talked to Brad, and wanted to clarify that the WCF RIA Services RC is only for Silverlight 4, and since Silverlight 4 RC does not have a go-live license, you should consider whether you need to support any current Silverlight 3 apps before installing on base hardware. You may want to install the SL4 bits on a test machine or VM.
The good news is that Silverlight 4 should release within a month, so there’s not long to wait before you can go live on the above releases.