With the iPhone 8 set to remove the hardware Home button, where is Touch ID to go? The power button, perhaps. Today, Apple was granted a cache of 68 patents, which hint at the possible new locations for the fingerprint reader. The Power button patent was filed in Q2 2015, while the Xperia Z5 came out in early Q4 that year - the first Sony phone to put a fingerprint reader on the Power button. Sony already disables this functionality in the US, anyway, which reduces the chances of a patent dispute with Cupertino. Apple patent drawings of possible new locations for Touch...
Source: http://www.gsmarena.com/apple_granted_patent_for_fingerprint_reader_on_the_power_key-news-25582.php