The Google Fit v2 API is coming to Play Services soon as a teardown of the most recent Google Play Services APK reveals as much. This isn't the only thing on the way though, it seems, as there is also references made in the code to FIDO refresh tokens. Google launched Google Fit and showed of APIs for the app all the way back in 2014, and while Google has made some updates to the API since then to allow for an improved experience for developers who are working with, it's been over two years since the launch of Google Fit and its API so it's not too surprising that Google should be launching a version of the API for developers in the near future, as well as a new version of the app for users.
In regards to the new API, data in the APK for Play Services reveals that users will be able to add a couple of new key elements to the general information about themselves within the new version of Google Fit when it launches, which include hip size and waist size. In addition to these new two new pieces of new information, it appears that users will be able to enter in other data too, like body fat percentage, blood glucose, blood pressure, blood oxygen saturation (a piece of information that users of some of Samsung's latest Galaxy phones will be able to take advantage of), body temperature, basal body temperature, and basal metabolic rate.
Users will also be able to track their hydration levels in Google Fit v2 which was already hinted at last Fall, and other stats like Cycling pedal revolutions, as well as data like ovulation test results and cervical position that will be fields which users can fill out. When it comes to the FIDO authentication tokens, it looks like the upcoming version of Play Services will allow Android devices to wireless support for the use of physical authentication keys for a single use scenario when logging into their accounts. If you're someone who uses a physical authentication key every time you need to log into your account, Google seems to be preparing Play Services to allow this type of authentication method.