SeekingAlpha speculates on why Sony needs so large capacity expansion: "If we look at the amount that SNE plans to allocate the device capex, SNE could have the option of expanding the capacity to 110k -120k wafer/month from the current 87k. At the end, this will bring total capex for the new capacity to JPY460bn or equivalent of SNE's total image sensor revenue for FY3/15."
The SeekingAlpha's guess "is that SNE's decision to add additional capex to the current level implies that the company is confident on securing a place as a integrated camera solution provider for an Apple iPhone model in 2016. There's a good chance that this involved SNE's dual camera module, a feature that has been rumored by the press in the past. I think that SNE is confident on receiving large order volume driven by its exclusive supplier relationship (as it has done in the past with AAPL), high standardization and the longevity of the component, all of which allow for economies of scale."