Any time I've asked someone from the company about the potential for a new 10mm pistol, I've gotten the same response.
While the 10mm cartridge is popular among a small element of enthusiasts, it's pretty much only generating interest among those willing to handload or those willing to pay the freight for custom ammo made by a few of the smaller ammo companies.
Believe it or not, I've been told that there are some serious aficionados of the 10mm cartridge among folks at the company, but that doesn't change the fact that the major ammo makers aren't reporting significant increases in demand for 10mm ammo. If the company uses sales of commercially loaded ammo as an indication of whether or not it might be profitable to make another 10mm gun, it might be a while before we see another one from them.
Another issue often raised is that sales of existing caliber handguns are booming, and production can't keep up with the demand for existing models/calibers. Why would they want to cut into their already heavy demand of existing cataloged guns to make something for which the demand isn't demonstrably as great?
I've little doubt that a new 10mm pistol could be produced in either (or both) the M&P or the SW1911/1911E lines, with a little R&D. The R&D may have already been done, but existing production and sales demands are too heavy to justify trying to devote manufacturing resources to something else. I've been told that the engineers often have some interesting projects in the wings, but it's up to corporate to decide when a product has enough demand to be a viable addition to the catalog ...
and a drain on the 'not-unlimited' manufacturing capabilities.
Maybe if the 10mm enthusiasts could manage to persuade the major ammo companies to start making more 10mm ammo, in more choices attractive to owners looking for hunting & defensive ammo, S&W might see an uptick in ammo sales and look to getting a gun out there to take advantage of the commercial ammo sales.
While there are more 10mm guns being made than ever before, the cartridge still seems stuck in the niche of being something that primarily interests handloaders, or owners wanting to buy custom , hot-rodded ammo made by smaller companies.
Just some thoughts, based upon what I've been repeatedly told in recent years when talking to various folks from the factory (none of the corporate/management strata, though).
Maybe if the new SIG Classic 10mm sets sales records, and SIG starts reducing production and sales of their other pistols/calibers in order to meet demand for the 10mm, S&W will see something of interest.