I remain both apprehensive and skeptical, and I desire more hardcore evidence before taking a stance.

I /will/ say, SE has a very long history, stretching clear back in FFXI's salad days, of spoilering new content with artwork or small mentions in the plot. The concept this and Thancred could be a spoil at something is by no means a tinfoil hat theory. But it simply can't be verified /yet/.