This might not make them the dominant power but it will make them a strong stable power. Sweden wins GNW with invasion of Poland, defeating the Russian threat, since Prussia and Austria are in a couple of major wars for the next few decades, could lead to Austria and maybe Prussia's demise. By the end of Stanislaw's rule, the Sejm would probably be removed due to Sweden's influence maybe through a war or ever weakening power of the Sejm until they are no more.