I believe social media is here to stay and will always be around in one form or another, after all it is just the online, easy method of something us humans are hardwired for - to be accepted as one of a community.
With the rise of the social media technology has come a new wave of web users with new browsing habits and needs. The older generations previously considered internet "geriatrics" (and I am one of these!) have found a new voice online and despite recent annecdotal evidence to the contrary, it seems teenagers are amongst the most active participants and fastest growing user demographic of some social media services.
What will change however is the way in which we interact with people online in the technology we use to do so and what we share with our network. As an example, a lot of people these days find their news in the links shared with them on social media sites rather than the old model of heading to one of the old content providers and looking for something interesting. Now your network posts a roadmap for you to get straight there. I also have no doubt that the "Next Big Thing" in terms of social media service is just around the corner. Any new social media technology is subject to the fickle tastes of the mass market and the possibility that tomorrow, people will be hankering after something new. It seems ironic that they are often subject to the very market forces they are designed to propagate.
That said, there are many exciting developments in the world of social media. Recent examples include the ability to take it everywhere with you via iPhone apps (being my personal favourite). And who knows what will be next? One thing is for sure; if the recent trends in inventiveness in methods to communicate and share information with each other is anything to go by, the boom shows no signs of abating any time soon.
In summary, social media is definitely here to stay however it is evolving so quickly, by necessity as well as by design, that it may have a very different appearance in the not too distant future.