You can generally increase diameter with dilation, but depth is usually more or less permanent (and Brassard, at least, says the labia don't count). Don't forget, though, that it's impossible to insert a penis like a dilator; bodies get in the way of the penis going in all the way to the base, so a 5" vagina can usually accommodate much longer penises.
Brassard also says "Gaining depth by applying more pressure is not advised," for what that's worth, but you should always listen to your own surgeon first.