I'd be greatly surprised, really greatly even, if the super star destroyer isn't included... it's one of the most popular starships from the whole star wars galaxy, it's impossible to include the 'oldie' victory destroyers and so on and then skip the mother of all capital battleships... The only question is whether it will be buildable or only available as a special appearance Hero ship. I'm inclined to think the latter, as the Executor from Ep.V-VI is made to look pretty unique, Vader's personal command ship. On the issue of size discrepancies, yes, there are several classifications of what a Super Star Destroyer is. The most original, from Empire Strikes Back, where by literally comparing the established 1600m long ISDs with the looming giant they're shown patrolling, we arrive at something in the 19,5 km range. This has been backed up by some EU stuff, but some say this was only the Executor's size, not the 'usual' SSD, which is usually listed at 8km long. Then there are all sorts of huge villain megaships that fall under the SSD category, such as the command ships from the Jedi Knight games, and then ships such as the Eclipse and Sovereign Destroyers can be viewed as SSDs, while their superlaser abilities might beg a different classification...