Is Symantec Web gateway is the replacement for Symantec Web Security?
Symantec Web Gateway does provide many of the same features you saw with SWG, Content blocking based on content/classification, virus scanning and more. But is currently a hardware based applaince that sits on the network, either inline or on a span/tap port.
Symantec Web Security was a proxy server/service. The Web Gateway requires no client proxy configuration for filtering to happen.