It's very much a living language, yes? So I think it will change and expand, like other living languages, but I don't see it disappearing. I think current technology has allowed hearing people who have never met or seen a deaf person to be exposed to the language and to Deaf culture in a way they never would have before.
Sign language is incredibly visually appealing and beautiful, even to hearing people who do not know anything about it.
I am talking about youtube, vimeo, shows like Switched at Birth, performing artists like Sean Forbes and Signmark (and probably others I don't know about), the involvement of people like Keith Wann in a national reading campaign. This wider exposure builds up interest.
I also think that more and more young parents are starting to use some sign with their babies. We use it with our mentally retarded daughter, who cannot speak, and we used it a lot with our seventh child, who did not speak until after he was two. It's not enough to sustain a full language, but it's part of the wider exposure sign is getting.