Glock's been doing the
10mm AUTO ... successfully for how many years now?
Large & small.
Plus, the CZ people have recently teased us with this possibility - an "experimental" 10mm CZ:
http://http://www.youtube.com/watch?v=iIK6cFPevmE
So seeing an M&P in 10mm wouldn't be at all improbable, provided the critical parts are engineered correctly (beefed-up) and the gun is properly sprung.
Gun-makers area always watching the handgun market for new ways to increase revenue, including the "niche" markets, like the "retro" market they tapped a few years ago for old-school 1911s and some S&W revolvers.
Hardly what most handgun consumers buy, but these guns still sell to a certain segment. Caliber-niches are part of this sub-market and, while small, are still sources of profit. There's certainly a niche market of dedicated 10mm who'd jump on an M&P chambered in this cartridge
and cross-over shooters from other calibers who'd buy a double-stack 10mm that's not a Glock.
Coming from a different direction on this issue, ... the Sept 2013 Am. Rifleman carried a positive review of the Turkish-made SARs K2 in .45acp. Built off the CZ-pattern, it's a big all-steel DA/SA using a double-stack mag.
After seeing that CZ "10mm" vid above, and noting what appeared to be the use of upgraded mags with the new (flat) floorplates that Mecgar makes for Tanfoglio's 10mm Witness-line, I ordered several 10mm Witness mags from Midway. EAA is the importer for both the Witnesses and, now, the SARS .45 K2, and there were already rumors that EAA has received some 10mm K2s from Turkey.
Well, the Meccgar mags arrived and sure enough the package was marked
"10mm - Witness/K2." They easily loaded 14-rds, although they might take 15, but I didn't want to muscle the last one in. Why would they also be marked "K2" if that gun in 10mm wasn't coming to these shores in the near future? They ran just fine in that "experimental" CZ 10mm - so, in theory, that's
3 - count 'em - 14-rd all-steel 10mm pistols of similar design.
Point being, with the Turks offering one, it's quite possible that other gun-makers (Ruger?) are considering bringing out something in a 10mm autoloader down the road.
Stay tuned, ...