Well, yes- you can, but I don't know what your question addresses. (Forgive if you already know all this)
Sound suppressors are governed under the National Firearms Act, which require payment of a $200 tax, fingerprints, photographs, and Law Enforcement approval at the local level, in addition to Fed approval.
So, once you go through that to get your suppressor, you then need a gun to thread it on to.
IF the ban dies, and there aren't any restrictions on threaded barrels and flash hiders, then yes, you can put it on a "new" AR10.
But as it stands right now, a sound suppressor must be attached to a preban AR, since
A) It usually requires a threaded barrel
B) Even though it's intent is to moderate sound, Suppressors are the most effective flash hiders you can have- so that adds another "evil feature" to the rifle.