The topic of why the .357sig caliber isn't very popular has been posted a few times on TFL.
If you review the older posts you'll see the # of reasons the .357sig didn't gain any support in the US shooting sports/LE.
Author & noted tactics instructor John Farnham carrys a SIG P229R in .357sig.
He said the round is powerful, feeds great & is very fast(high vel).
I didn't read or hear that S&W ended the M&P series in .357sig for the general public.
I saw it on S&W's main website in both the full & compact size.
I also see them listed NIB(brand new) on GunsAmerica.com & SlickGuns.com .
I'd carry a .357sig on duty or as a CCW if I had the $$$ to get a good brand like a HK or SIG Sauer.
The only serious -s I've ever heard about the .357sig is the noise(blast) & the recoil. I'd think proper training & shooting methods could overcome those problems.
Clyde