Would the phrase "What Say You" ever be correct grammar?

The older phrase was actually "What say ye?" but was replaced by the slightly-more-modern "what say you?" a century or so ago. Before the "do" construction was exclusively used in English, we used the reversed noun-verb order in some question forms. We now use "What do you say?" to mean the same as the older "What say you?" The reversed noun-verb order is still used in some other languages (such as Scandinavian ones, which have had an influence on English) to this day.