In a perfect world, the phone you buy would get relevant and timely updates to add new features and fix security issues for many years after the initial purchase. Sadly, such a world does not exist (though it's easy to understand why in some cases), but at least people who purchased the 2016 Samsung Galaxy J3 (J320A) from AT&T have a significant upgrade waiting for them. The phone is getting Nougat 7.1.1 and the update includes the BlueBorne patch.
A year-old entry-level phone getting this kind of upgrade, late though it may be, is quite astounding. The J3 of yesteryear launched in May of 2016 for $169 outright, or $5.67/month. Owners of the device can look forward to many new features, like multi-window, an improved Doze mode, better notifications, and other improvements — not to mention the August security patch (a few months behind, but at least the BlueBorne fix is present).
Build number NMF26X_J320AUCU3BQI5 clocks in at 1GB in size and should be rolling out to users now. So if you're still holding onto one of these, be looking for that oh-so-amazing update notification.