Yea....its relatively new, but already a year old on the iOS side of things (which alot of people take a dump on for being slow to adopting new things). Plus if HTC thinks its good enough for the mid end, why not for a Galaxy 4 high end next gen device?
It's better to release 64-bit right versus rushing it out with iPhone 5S that suffered from blue screen of death crashes, low memory crashes and still suffers from app and browser tab reloading when task switching due to low 1GB DRAM. There's also no convincing data that shows 64-bit app performance better than 32-bit.