There is no way to know until they get to where they will be...sorry for the BFO, but that is the way of it. It is not the "projection" that will make them appear big, but the side growth. I am a B cup now, but they do not stick out any further really, maybe only a little. Where the size came in in that they filled in out the outer hemisphere.
I spoke with my endo about the development stages for me, I am starting this again later in life. During my last exam, she pointed out all of the "solid" that is now obvious underneath...the ductal and lymphatic development. This will be filled in with fat and she explained that the size is really an unknown for a few years. Up until then, it is really hard to gauge where things will end up.
No matter what, enjoy your body where it is in the "right now". It is wonderful!