How big will a black lab / (australian?) shepherd mix puppy get?

ercup is about 14 weeks old and is 15 lbs right now. She seems kinda small for a german shepherd, so I'm uming that she must be australian shepherd (we're not sure - she from the pound). The lab part is definite. She has a very silky solid black coat and everyone said she looked like a full breed lab when we got her at 8 weeks. Now we're definitely seeing more shepherd (I guess) - ears are more perky, snout longer, etc. She's a great puppy - whatever she is and however big she gets!