Normally the kind of customer who buys a "rugged" phone like the Hydro VIBE isn't all that concerned with having the latest and greatest in software - or at least that seems to be the attitude of the carriers and manufacturers, who don't seem very concerned themselves. Perhaps that's why Sprint and Kyocera launched the phone with Android 4.3 back in May, despite the fact that 4.4 had already been available for seven months. The company corrected that oversight with the 2.033sp update, dated yesterday.
Exactly what version of Android 4.4 the update contains isn't clear - Sprint's support page just says "KitKat." Other changes include support for Sprint's Wi-Fi calling system (which has already been turned on for most of the carrier's high-end devices), fixes for the camera's auto-focus and attaching videos to MMS, and a slight change to the signature system in the built-in email app. The size of the update hasn't been disclosed, but it's probably going to be multiple hundreds of megabytes, so find a handy Wi-Fi hotspot for a quick flash.
Sprint tends to stagger its software releases, just like all the other American carriers, so don't be surprised if your Kyocera phone doesn't get the over-the-air update alert for a few days. At least a few XDA members have gotten root on the budget phone, so if you're one of them, the update may not flash on your hardware. If it does go through, you'll probably lose root privileges.