I've worked with one of my customers with a similar multi-petabyte environment (higher education) who had similar hopes. They got pricing from two vendors - one who did an "in data path" solution, and one did an "outside data path" solution.
The licensing for both was per terabyte, per year. They looked at those prices, added to the price of "commodity" hardware capable of storing several petabytes.. and it was cheaper to just buy FAS shelves.
Your mileage may vary, but.. I don't suggest you hold your breath. I know one of our US higher ed customers has elected to use this sort of software, but they do it for data management, not to reduce costs primarily.
