In another patent application describing stacked BSI sensors, canon looks to solve problems with high melting point metal is moved from being on the sensor substrate to only on the peripheral circuit substrate. They are concerned that the high melting point metal will diffuse into the photo diodes collecting image data.
There is clearly a trend that Canon is looking to solve what they feel are issues with stacked BSI sensors, and certainly because they plan on actually implementing them one day. Of course there's no timeframe for this, it could take years, or Canon could be rolling them out this year.
There's no doubt about it that especially for mirrorless, stacked and BSI sensors are very important. Firstly because of the performance, and secondly because it improves the ability to collect light at high incident angles.