Remember Napster, the first widely successful peer-to-peer file-sharing service? In 2001, the Recording Industry Association of America won a lawsuit that killed Napster as a free service.
Lawsuits against Napster did not shut down peer-to-peer file-sharing because, like Wikileaks, Napster was neither the source nor the ultimate destination of the information flowing through it.
Wikileaks is a peer-to-peer file-sharing service. Its current architecture is centralised, which is a weakness that it shares with Napster. But if the central node is taken out, it won't be long before a new service with a decentralised architecture springs up.
The only thing that shutting down Wikileaks could possibly achieve is to make whistle-blowing slightly less convenient. For about a month.