A new update is currently rolling out for Galaxy S5 users over at Sprint carrying the build no. of G900PVPU3BOK4. The OK4 update brings some performance improvements as well as minor UI changes along with bug fixes and security patches.
Right now, we don’t have the OK4 firmware in Odin’s TAR format with us, so, OTA update is your only way to upgrade your Sprint Galaxy S5 to OK4.
If you were hoping for Marshmallow update on Sprint Galaxy S5, then you would have to wait for another 2-3 months.
Going by the Lollipop update’s experience, which was released in October 2014 and released for Sprint S5 on February 5, it’s fair to say first week of February 2016 is when Samsung could release the Android 6.0 Marshmallow update for the device.
You think that’s a long wait, well, buy a Nexus device next time around. If you could. Till, then that’s how Samsung updates roll, which is kind of disappointing, but totally expected, even if not acceptable, now a days.