If I understand this right, no, the curse has never been removed. Sam’s been small the entire time ever since that one fateful day. Whether it gets removed or not will most likely be the culmination of the series and the focus of their struggle against Celeste.
If Sam gets his size back for a bit or gets to see Dean eye to eye, he will not let big brother ever forget who’s the tallest between them. Of course, if he ends up back at his normal size, he’ll probably get buttoned up in a pocket if he keeps poking the bear.
Brothers Apart 