Assault Weapons Ban Renewal - "between" guns

For the sake of discussion, lets say the AW ban gets renewed on Sept. 15th.

Will this "gap" without any AW ban allow all the firearms made 1994-2004 to become essentially "pre-ban"?

That depends completely upon how it is rewritten. The legislators can do anything they agree upon :p

I'd doubt that they would do that, though. They would probably leave the grandfather clause as is.