Apple unveiled the rumored 12" MacBook with Retina Display this week. The leaks Mark Gurman reported were largely accurate, but another report claiming it would include a Touch ID sensor was not. I don't believe Apple will ever include a Touch ID sensor on MacBooks because it doesn't make strategic or financial sense to do so.
The primary use of Touch ID on the iPhone and iPad is to unlock the device. It is also used for Apple Pay and App/iTunes Store purchases. Using Touch ID to do this on the Mac would be welcome, but I think Apple will solve the problem another way. They will enable unlocking of the Mac through Apple Watch or through the iPhone's Touch ID sensor. This will provide an additional incentive for consumers to purchase multiple Apple devices while also enabling a new feature in the Mac without raising costs.
This may annoy some people, but it shouldn't be a major issue. There are many more iPhone users than Mac users in the world, and a large portion of Mac users likely already have an iPhone. It may even be possible to bring this feature to older MacBooks through a software update, which would be a welcome addition for the millions of iPhone 5s and 6/6 Plus owners out there. I believe this is the same reason Apple hasn't introduced a Mac with cellular radios, it's already possible through millions of iPhones.