The current client is 25GB. That includes 5 'maps' or 'instance zones' and about 30 of the smallest ships in the game. Making a guess based on the number of announced ships and locations, that's less than 1/10th of the planned 'content' for the game.
Currently when the game patches it downloads EVERYTHING again, and overwrites the directory. The compressed 'patch' file is typically 20GB. This is still very early in the game development. I'm sure they'll start optimizing their patching at some point.
The did make a casual forum statement about the size of the client and 'optimizations of that' Basically, "don't hold your breath." While they will reduce the size of the content as much as they can, they will be adding much much more content, so any optimizations will be overcome by the sheer bulk of what's coming.
Star Citizen is not skimping on the detail of their game. They've probably pushed that so far that their strength has become a weakness...but it's sure pretty.