It is not (directly) dependent on the manufacturer. It's dependent on how many barriers your manufacturer and/or carrier put between the original Android sourc

It is not (directly) dependent on the manufacturer. It's dependent on how many barriers your manufacturer and/or carrier put between the original Android source, and your phone. In the case of HTC phones with Sense, they have to add a lot of engineering work between "Android version is available" and "that version has Sense added". They need to make sure all the hardware drivers still work, update them for updated kernels, etc. If the phone is a "Google Experience Device" then it's very close to the original source, and should get updates sooner than the rest.