Sure, if they could make something in the M&P pistol line to fill the gap left when they discontinued the CS9/40/45's, I'd probably order at least one of them.
After they'd been out in the hands of shooters for 1-2 years.
The CS45 had a 3.25" barrel, the 4513/457 was 3.75" ... but the smallest the M&P 45 goes is the compact with a 4" barrel (making it pretty much akin to the 4513/457, albeit the M&P has 8-rd mags). Maybe a 3.25" M&P 45sc would be a good idea?
The hypothetically half an inch reduction in length of a M&P 9/40sc might not seem like much, but the CS9 felt lighter and smaller in the hand than the CS40/45's.
Maybe they could more easily shoehorn the .40 into a small 9mm frame/slide, unlike when they were having to use the alloy .45 frames for the 4013/CS40 for strength (although the short-lived 4040PD, with its Scandium aluminum frame, for greater strength was the exception

). I'd think the plastic frame concept, utilizing an integral steel sub-chassis and a steel locking block, ought to mitigate such concerns, though.
Nice thought.
I haven't heard anything, myself, but the company has become really good at keeping such new projects under wraps in recent years. They weren't even dropping subtle hints about the M&P until it had apparently been underway for at least 3 years.
Now, if they decide to go the way of the Bodyguard pistol line for a smallish 9mm? I'm not sure that would interest me so much. That's a "busy" little pistol (inside the frame). Not so sure I'd be interested in a 9mm version until they'd really ironed out any remaining kinks.
Maybe a .40 Bodyguard would serve to bring any remaining design weaknesses to the surface ...
