This question was recently asked at my workplace that caused me to pause to a moment. Sure S&W is famous for their legendary wheels guns, but when I think of M&P I first think of their semiautomatic pistols.
Founded in 1852, Smith and Wesson as a company made great company profits from the sale of weapons during the U.S. Civil War (1861-1865). Revolvers dominated for decades until the appearance of semi-auto handgun in the late 1900s. Eventually police departments switched from traditional revolvers to semi-autos in order to keep pace with criminal firepower. In 2005, Smith & Wesson debuted a new polymer-frame pistol intended for the law enforcement market.
The Smith & Wesson M&P (Military and Police) is mainly a polymer-framed, short recoil operated, locked breech semi-automatic pistol introduced in the summer of 2005 by the American company Smith & Wesson. It uses a Browning-type locking system. While targeted at law enforcement agencies, the M&P is also widely available on the commercial market. The M&P revolvers are the exception to the polymer frame lineup.
Of the aforementioned M&P models, S&W lists 88 version on the Internet catalog of which only 3 are revolvers. I guess even today there are still those shooters that prefer the reliability of the revolver. S&W offers these guns as either 357 magnum or 38 special +P versions in the N and J frame configurations.
So the M&P lineup of pistols does include revolvers, but it's only 3% of the handguns listed in their current online catalog (2/23/16).