The sensor is more than just BSI. Samsung call it ISOCELL, and while it seems promising, I will await some techical measurements from the likes of DxO.
"ISOCELL technology forms a physical barrier between neighboring pixels – isolating the pixel. This isolation enables more photons to be collected from the micro-lens and absorbed into the correct pixel’s photodiode minimizing undesired electrical crosstalk between pixels and allowing expanded full well capacity (FWC).
Compared to conventional BSI pixels, the ISOCELL pixels decrease the crosstalk by approximately 30 percent which results in higher color fidelity to reproduce the original color with sharpness and richness, and increase the full well capacity (FWC) by 30 percent which leads to greater dynamic range."