User blog comment:Omega natsu2/Chapter 413: The Book of E.N.D., Predictions./@comment-115.147.116.67-20141209085540/@comment-4829046-20141209091642

Already discussed this and doubtful. God Slayer Magic is ancient(even though one can learn it by spending a day reading a book....) while we have no clue about the 4 gods of Ishgal. I assume that it is a relatively newer term just to hype them up as no longer being human and having magic rivaling gods.