The problem with this question is that SEO as we know it is destined to be obsolete. Optimizing various data and media formats as well as ongoing promotion (not just link building) is what will characterize successful "SEO if you want to call them that" shops in the future. 

I don't see why those kinds of organizations can't achieve major player status just like the large management and IT consulting firms have. A combination of software, process and brain power consulting.