Interesting question! I'm going to hazard a guess and say something like Twitter will probably be around for a long time. 20 years? Possibly not, but it is going strong and changing, which is important. Recently I've been looking at the usage of social media in Journalism, and Twitter is becoming both a more valuable resource to journalists (in the way content is filtered and distributed) and also a useful way that they can saty in touch with the general populace. So I think Twitter will stay online, but probably change into a more professional site. Secondly, as said by cody below, Google Thirdly, I'd guess news sites such as BBC News, Sky News etc, will continue to be around online in 20 years, in fact, newspapers will probably have a stronger online presence by this point than print (even now, it's pretty close). I'm not sure what else, but the internet is an ever changing beast so it's really hard to predict what will happen as trends come and go!