It may have been delayed but there is a Nebula in game at SOL. If you want a peek at it, It's in one of the ship docks. When you enter SOL you'll be facing the station. Go "left" and you'll see another station out in the distance, there will be a string of docks in a line between the two stations. The Nebula is sitting in the 3rd one I think. I was in SOL 1 when I saw it.
I took some screen shots but I'm not at home right now, can't post them up.
As a Klingon, I have destroyed at least three Nebulas in the D'Kal Star cluster exploration area. The sprite is in the game. It did not describe the type of ship it is. It registed as "Federation Nebula Class".