Social media marketing is about to become just marketing. I don't think this is a revolutionary statement by any means. I do believe that while most companies are hiring someone to do social media in conjunction with brand managers or marketing managers, the time will come - hopefully soon - where social media marketing is just a part of the marketing manager's job.
Social media should be fully integrated into marketing strategies & plans. It shouldn't be an afterthought or an add on. Social media marketing takes the brand's marketing plan and executes it across different channels. That's it.
I know by making these statements I may be writing myself out of a job in the future, but I do think that true marketing managers in this new world of marketing need to holistically incorporate social media marketing, print advertising, digital advertising, point of sale marketing materials, influencer outreach and blogger relationship building (brand ambassadors!) into their marketing plans. I don't think it's optional. The marketing managers who do this now, or start soon, will be way ahead of the pack. There's a reason they're called 360 campaigns...
Where I see current social media managers moving is into a more of a "digital edge" role: keeping up to date on new technology, guideline changes, law changes, optimization, digital advertising, and anything else that teeters on the line between tech & marketing. Digital marketers can assist brand marketers in executing brand plans across all channels, tailoring the plans to each platform.