Will there ever be an expansion for SW Galaxies that has at least, half of the important parts of Coruscant? And then a Part 2 for the second part? It all makes sense.

Nope. That will probably never happen.

coresant is to complex with it's engineering so I'm sure that wont be ingame.

However, there has been discussions of including some of the most important places of Coruscant as 'theme parks'. The emperors throne room, things like that. You would not be able to go outside them, like on a planet, but you would in a way be able to go to Coruscant. This is, however, far into the future, at the earliest in the expansion after the space expansion (we're talking about 2 years from now).