As this post is already quite old, I wanted to update it:
(Spoiler: It's not gotten better.)
This is fantastic news. Really.
We're finally getting an official version of KitKat.
We're as good as a quarter of Android devices registered on Google Play.
And we're even better than a sixth of Android devices registered on Google Play.
We're worse than 60% of Android devices registered on Google Play.
(It's not going to get better in the future by itself.)
We're getting security fixes - up to January and counting.
We're getting support for the new notification system, BTLE and Android Wear.
And this is a three year old phone.
Well, I already had most of these things - thanks to @chrmhoffmann.
This is good for now. (And is probably going to be fine for the next months.)
But this is nowhere near a long-term or even a middle-term solution.
The percentage of KitKat is going to further decline. About 60% of Android devices registered on Google Play already have a newer version of Android.
And those Android Security Bulletins aren't going to come forever. At some point in the future, Google will abandon KitKat.
I know that we are in no way entitled to receive Lollipop, Marshmallow or Nougat. But in an ideal world, we would.