I agree that that's what Arduino thinks the market is, but I disagree that their conceptual market will buy this.
Arduino-branded hardware is typically 5x the cost of the clones (remember, it's OSH) at no noticeable improvement in quality. DIN-rail mountable arduino clones and modules with I/O isolation that run on 24V power already exist at very reasonable price points, and from reputable dealers such as Automation Direct. I've used ruggedized modules such as Industruino (although their prices have definitely gone upmarket) and they're nice. IME, the only people who buy actual Arduino hardware are either beginners who don't realize that the much less expensive clones are every bit as good, or business buyers who don't really care, because it's not their money.
But maybe I'm wrong and there's enough of a price-insensitive market to make this a success. I certainly hope so. I'm a freelancer, so the bigger the market, the better for me :-)
I have designed & built an arduino clone-based product that mounts on DIN rail because the hardware it communicates with also does. Multiple installations running large machine control applications without a hitch. The clones are fine.