It picks up right after MMX ends, and you definitely end up in a new land. I think you take a ship to get there but that's entirely in the prologue - the actual content opens with you already there (avoiding spoilers). AFAIK there has never been any other sequel add-on.Also, it wasn't always bundled with the original MMX, it was released as DLC some time after. But MMX always had problems with its DRM: incorrectly locked areas, and missing inventory items that were supposed to be included with premium editions. So at some point Ubi abandoned all attempts at DRM and released everything for free. This included the premium edition items, TFatU sequel, and a couple of other DLC dungeons. GOG version has been sold like that for at least 6-7 years - can't speak for Steam