I'd say sell now... The NFA, GCA, and Hughes Amendment are fixing to get destroyed by the Supreme Court very soon, thanks to Matt Hoover's Auto KeyCard case (and several other cases like the Bumpstock case) that are heading to the Supreme Court right now, and the GOA and FPC's lawyers challenging the NFA on face-value of Constitutionality based off the Bruen case's clarifier of having to prove "text, history, & tradition". So, the old phrases, "Sell your truck while it's still running..." and "Buy low, sell high" should apply appropriately. If the NFA and/or GCA get obliterated by the SC, then price values of NFA items are going to plummet, because new production units will be widely available once again (pre-86).
Personally, if I had any, i'd just hang onto them. Then again, I was born 11 days before the ban...So, I never got to experience the free world. Although my dad had a few friends who had a bunch of them, so I got to shoot them growing up in the 80's and 90's.