The Wi-Fi Galaxy Tab S 10.5 got Lollipop back in March, but it wasn't until a week ago that the carrier variants started receiving OTA updates. AT&T was the first to roll one out, followed by T-Mobile several days later. Verizon announced its update yesterday, and now it's Sprint's turn. Samsung has posted the changelog.
The update bumps the tablet up to software version T807PVPU1BOE3. As for what changes are in store, well, you're the last in line. Surely you've seen one of the other kids playing with theirs by now. You're getting what they have.