You and I must be living parallel lives, I just bought a 2016 with 68K on it today! What color/package did you get?
So, I remember reading that while Toyota guaranteed the batteries through 8 years/100K miles (whichever comes first) their batteries lasted much longer (surprise, surprise). I'm going to try and source it but I've read about people with Prius's lasting 150K to 200K and sometimes more. I think, at a minimum, you should be good for a while.
Yes, it's 8years or 100,000 miles for the hybrid battery. My Prius battery when out @6 years and ~97,000 miles and they replaced the entire thing under warranty so its like you get a brand new car all over again.
For the Prius it may be because I tried a lot to stay on the battery in town and would feather the throttle to prevent the ICE from turning on. So I may have caused it to wear out quicker. I believe if you drive the car normally the battery will be fine.
2012 MY. It was 261k miles and -11 years before I got the first HV battery CEL. Coincidentally that was also the first year I began to park the car outside over night and within 4 months I received the CEL. I think it didn’t like the extreme cabin temps.