Yeah, I also thought S&W was giving up a part of the market they should've worked harder to keep active, meaning the metal-framed traditional double action models (TDA).
That task has mostly been left to Sig Sauer, oddly enough. The ironic part is that not only is Sig continuing to make metal-framed TDA guns, but they've also essentially duplicated the short SA trigger reset of the S&W with their SRT (Short Reset Trigger) option. (We were told in a class that the SRT sear & sear spring was developed when Sig was competing for a large LE contract and wanted to have a similar SA trigger reset to the S&W gun, which was their competition - and which was awarded the contract, form trivia's sake).
A big problem with continuing to offer the metal-framed TDA guns was the cost involved. There's no way to reasonably compete with the reduced cost of polymer-framed pistols in a competitive market. The metal guns just cost more to make. The cost of the CS series was becoming pretty steep when it came to their MSRP, as well as what dealers were able to finally charge. More expense, less profit. Do the math.
I'll grant that the M&P 45c seems as though it will make for a reasonably decent substitute, size-wise & capacity-wise, for the discontinued 457 and even the 4513TSW ... but the only .45 close enough in overall size to the the smallest of the previous .45's, being the diminutive CS45, seems to be the newest of the SW1911 series, and not everybody wants a 1911-style pistol when it comes to a subcompact .45 pistol.
Oh well. Time marches on ...
I do prefer my CS9 to my CS45, all things considered, but I have no plans to get rid of my CS45, if only because I think it represents an interesting execution of concept when it comes to a reliable, small metal-framed TDA .45 pistol.