I'm an Asimov reader (though it's been a while). My favourite "virtual presence" SF, though, has to be Snow Crash by Neal Stephenson.
I think virtual worlds will be increasingly significant. I'd put it at about 5 years out. I'm not sure, however, what the future for Second Life will be. My personal expectation is that new, significantly improved players will move into the space and take it mainstream. Sort of like MySpace and Facebook did with social networking. Second Life could very easily by the Friendster of virtual worlds. It's a little too clunky. As Pam mentioned above, it was a great way for her to extend her technical learning. But its successor won't require that. People don't have to learn so much to use Google, WIkipedia, Facebook, WordPress, etc.
So, I'd certainly recommend trying it out, learning what virtual worlds can be like, and thinking about how they can be used effectively. Virtual worlds are probably here to stay. But I wouldn't count on Second Life being around for the long term.