As much as I like my Sigma 24 1.4 Art and 35 1.4 Art, Sigma's new lenses confuse me. The 24-35 f2 being case in point. I do not know one person that has bought one. It may, or may not be, a great lens, but the focal range, size and weight just make no sense to me. The rumoured lens for Dx falls in the same category for me. If I used 50mm more, I would seriously consider the 50 1.4 Art. I would be much more likely to reach for the 58 1.4 , 85 1.4 (or 1.8 ) and an Ai/Ais 105 or 135.
I agree that Sigma have upped their game but I might have jumped at the Fx 135 f2 OS Art that was rumoured for so long. Even the oft rumoured 85 1.4 Art might have made me think.
If Dx keeps improving to the point it can be used for less than good light, at indoor sports/events the lens at 75-150 at 1.8 may sell.
I think some of their lenses are produced just to show they can make them
Tom