We've been trying this theory out for more than a half century, to no avail. The cubans I've met in America are some of the kindest, most fun loving people on the face of the Earth. Their country deserves a chance to import and export more goods for the betterment of their society.
No, sanctions on Cuba are putting them in a position where they have to create a democratic nation sooner or later. It might take time, but the sanctions are making it harder for Cuba to exchange, trade, import and perform business with other nations. As this procedure is taking place, Cuba is taking pressure and is forced to Democratize. It might happen or never happen. It depends on how stubborn or not the people and the leaders.