Board Thread:Movie Discussions/@comment-3542924-20151014222507/@comment-1030114-20151017070230

The King of the Monsters wrote: People can speculate all they want, but it doesn't change the fact that Kong won. The movie went out of its way to show that Kong won, and Toho even explicitly stated that Kong was the winner in a press release. Fan theories about what happened to Godzilla do not override official canon.

This. In addition, Toho probably set up the ending the way they did so that they could produce more Godzilla films - by leaving his fate ambiguous, it leaves audiences excited and wanting more.