If you rent movies from iTunes and stream it to your new Apple TV  and it never starts 24h/48 hour countdown, which means you have a long period of 30 days to enjoy them as much as you want. When you watch the movie on the new Apple TV, no warning appears.

Note: If you try to watch the movie through iTunes, it will trigger the 24/48 hour countdown.

It is sure Apple will patch this loophole on the new Apple TV iOS firmware or on the iTunes itself. So take full advantage of this bug until Apple releases a fix for this bug.