But why would Adobe still be labeling it (2015) if I'm paying for frequent updates and it's 2017?
I'm guessing is that it's because LR is still available under a perpetual license. When the perpetual is 're-offered' as a new product, all the new features since 2015.0 will be incorporated. At that time, they'll likely change the year number. So it might be LR 7/2017.
Although, to clear things up.. There have been exactly the same number of upgrades between the perpetual and subscription - slightly over 9 (there were some 6/2015.x.
x versions). After all, they are the exact same program. It's only the license that determines which features are
available to adjust - the perpetual 6.x will still show adjustments made by the new tools in CC2015.x. ... IOW - CC gets the new features, while the perpetual only gets bug fixes and new camera & lens support.