They saw the handwriting on this wall a long time ago, that's why the big soda companies have been expanding into non-soda beverages and even non-beverages. Check out these products lists, I don't think they're worried about soda's market share very much.
http://www2.coca-cola.com/brands/brandlist.html
http://www.pepsico.com/PEP_Company/BrandsCompanies/index.cfm
They've learned how to make suckers pay a dollar for a bottle of Dasani and/or Aquafina, which is a much more lucrative market marginwise than soda ever was.