Asking about the future of SEO is like asking about the future of Marketing.
Traditional marketing has changed so much, adapting to new routes of delivery, appealing to an increasingly sophisticated audience, finding new way to get the message noticed and selling product, even if the product is rubbish - just look at Justin Bieber, how the hell did that talentless git get so popular in such a congested market?
SEO, like Google, will and must adapt. As SEO techniques become more sophisticated, so too will Google. As Google continues to find ways to identify Black Hat techniques, so the Black Hat community will do stuff differently.
And then, just possibly, while Google is focused on doing all that, another SE will launch that takes a new approach (the modern day equivalent of Google coming up with PR) and the rules will all change overnight - Google will be too big to react quickly (like what happened to Microsoft) and the new upstart SE will become the one to use, gain traction and spawn a whole new generation of Black Hat tools.
The future of SEO? Constant, changing and increasingly sophisticated. Oh, and of course much more focused on Social Media and Local Search.
All of course just IMHO!