Sprint has posted the change log for an over-the-air update with the Galaxy S4 Mini's name on it. The release will provide the smaller version of 2013's flagship Samsung handset with international Wi-Fi calling and a couple other niceties. It will bump devices up to version L600VPUBNJ1.
International Wi-Fi calling lets Sprint customers dial folks outside of the US using whatever Wi-Fi signal they can get their hands on. However, calls are only free when placed to Puerto Rico or the Virgin Islands. Sprint will still charge its usual rates to contact numbers in other parts of the world.
This OTA also comes with a security patch and HD Voice icon support. As usual, look for it to go out in stages. An update isn't necessarily coming to your device right away just because Sprint has posted the change log. Usually, though, these things arrive within a matter of days.