It was strongly hinted at in Action Comics #2.
But from the Superman panel at the New York Comic Con, panellists confirmed it.
In the DC relaunched universe, Krypto, now Jor-El’s dog, did not make it to Earth alive.
Weep, dog lovers, weep. He will join Laika in spacedog heaven.
But you will get to see him rarther fine, large and powerful form in upcoming issues… hooves and horns and all.