ATI is planning on permanentally attaching a barrel extension ("fake noise suppressor") to the MP40, so that it would not be classified as a SBR and legal for importation for civilian sale.
I know the $200 tax really deters people, but I'd much rather have it as an SBR. A fake can on an MP5 look alike doesn't look that off. On a MP40 look alike, I have a hard time imagining it looking nearly as natural. It will be interesting to see the final product.