I never argued that device makers will make fully open drivers. I argued that if Ubuntu on phones becomes popular that "native" drivers will come. Drivers can be native and closed as they currently are on x86 Linux. Currently Tizen, Ubuntu Touch, and Sailfish use libhybris to leverage Android drivers. Native drivers would perform better. On the issue of open source drivers those will come when manufacturers realize that communites can do much of the work for you of creating drivers and open drivers open new markets.