My local gun shop just took a delivery of a SIG MPX with a brace from GunPoker. Called the prospective owner and told him, on the advice of ATF, he could toss the brace and the owner could pick up his pistol, OR, he could separate the pistol and the brace and turn the brace over once shown an approved tax stamp for a SBR.
Owner picked Door #1.
Hopefully the court case moves along.