The long-awaited new Apple TV must finally show up in September, in the same launch keynote as the “iPhone 6s”. Who launches the new rumor John Paczkowski, from BuzzFeed (who was from Re / code and, before, AllThingsD).
The "delay" in the arrival of the product allowed Apple to polish it even more, but what is expected has not changed: we will have updated hardware, thinner, with A8 chip, a new remote control with touchpad and probably an updated operating system with support to apps and the arrival of Assistant Siri.
What has been said recently that this new Apple TV * will not * support 4K resolution. But nothing prevents Apple from enabling it in the future via software.
Today's rumor also states that Apple shouldn't be announcing its new streaming of videos with the hardware, leaving it for the end of the year or maybe only for 2016. It still depends on pending agreements with broadcasters, producers, etc.