Question time on the stream this morning unfortunately confirmed that the item limit increase is only for inside. They won't be increasing gardens, but will look into it later.

The keynote yesterday also confirmed that the new housing area WILL be available from launch of 4.0 so we'll be able to go to it/walk around etc, but we won't be able to buy anything until a later (not yet revealed/decided) date after players have had a chance to play the main story.