Is the M&P design strong enough to handle 10mm?
Sure seems to me it's just as strong as a Glock--but if you take an M&P 45 design and slap a 10mm barrel in it, you've got that extra meat to work with. There's little doubt in my mind they could build a real winner with no trouble.
Maybe, eventually, but it may take a while.
Here in NC, the NC Highway Patrol tried the M&P .357 for a number of years, starting in late 2009, and had with problems with extraction and feeding. It wasn't noticed immediately. S&W sent their engineers and experts to NC, took guns back with them for evaluation and testing, tried all sorts of things, and were unable to get the M&P .357s to function properly.
In 2014, the NCHP switched to the P226 in .357 SIG. They are focused on that round, I think, because they believe it does a better job of going through windshields than most LEO-carried calibers.
S&W isn't currently offering any M&P in .357 SIG. IF you go to their website, every M&P-related .357 SIG model has the following statement added to the product description, and the overall entries are marked "ARCHIVE."
No longer in current production, content is subject to change and is provided here for reference purposes only.
If S&W figures out how to resolve their .357 SIG problems with the M&P, they may move to a 10mm version. But, if S&W can't get the .357 SIG round to run properly in the M&P design, I suspect they'll be wary of trying it with 10mm. While they have gone to a .45 version of the M&P, The .357 SIG and 10MM rounds operate at much higher pressures than the .45 ACP round, and it may matter WHERE that "more meat" mentioned above is positioned, if the lack of meat is a factor. I don't think many LE agencies will move to 10mm, and the trend seems to be in the other direction: a number of law enforcement agencies are moving from .40 and .45 GAP
to 9mm. The LE market is a big and important market for S&W.
Military units, even Special Ops teams, apparently haven't used 10mm handguns that much in combat -- preferring their long guns (some of which aren't THAT long.) LEOs aren't willing or able to carry even a small carbine in their work day, so an effective handgun remains their primary weapon of choice -- but even then, handguns are used far less often than other tools available to them.