The Firearms and Ammunition Technology Division (FATD) stated that it is working on two monumental determinations regarding modular silencers and vertical/angled foregrips.
https://blog.princelaw.com/2017/08/03/breaking-news-atf-to-issue-two-monumental-determinations/
https://blog.princelaw.com/2017/08/03/breaking-news-atf-to-issue-two-monumental-determinations/