User blog comment:Omega natsu2/Chapter 369: The Place Prayers Reach, Predictions./@comment-6904925-20140124110035

Silver is defiantly future Gray, after saying Natsu name, most likely the reason he is a demon, is similar to Rogue, he changed after Frosh died in his time a year later, it appears the same thing happen to Gray, he probably lost someone else important to him (Juvia most likely), maybe at the same event.