An update to a Korean ratings board listing today indicates that a "Sun Moon, Pokemon Special Trial" could be on its way courtesy of Nintendo.
Though no specific release date was given of the listing and no official announcement from either Nintendo or The Pokemon Company has been provided, a trial version wouldn't seem unlikely, as Pokemon Omega Ruby and Alpha Sapphire both provided demos tied to special offers prior to their release.
Pokemon Sun and Moon will launch for Nintendo 3DS on November 18.