Whenever Apple launches an impactful new technology, it tests everything well before expanding its appeal to other products in the line. How Touch ID, for example, it was so.
Launched with the iPhone 5s, the Touch ID was ?only? to unlock the device and make purchases in iTunes / App / iBooks Stores. Today, however, it has been expanded to the iPad line, the basis of Apple's mobile payment service (Apple Pay) and can also be used by developers in their own apps (for example, we have Bradesco and Banco applications Brazil, where we no longer need to use passwords to access financial information). It would be great to see this technology coming to Macs as well, right?
According to apple.club.tw (Google Translate) that has a history of success, as when it released photos of the iPad Air 2 and the A8X processor, this could happen as follows: while the new MacBooks would have a Touch ID above the trackpads, a new generation of Magic Mouse and the Magic Trackpad would have the sensor on its entire surface, making the feature compatible also for those who use Macs on desktops.
I honestly didn't quite understand how this Touch ID would work on top of the MacBooks trackpad, especially considering that the Magic Trackpad would have the sensor on its entire touch sensitive surface. Because of this (after all, the technology is the same), it would be much more plausible to have the same thing in MacBooks (a fingerprint sensor taking the entire length of Apple's trackpad covering this is not lacking).
Taking into account that the Touch ID is now not only used to unlock the device, but also as a means of payment and a way to interact with third party applications, something like that would make a lot of sense.