Welcome davidkay, and congratulations on your first AR. In a week I`ll have a Colt 6400c to my name too.
When/If the 94 AWB goes away, it really shouldn`t effect the value of a postban firearm. Because you will then be allowed to install preban feature on your M4. Such as a colapseable stock, flash hider, and bayonet lug.
Preban firearms will/should drop in price because basically after the AWB goes away, most of them will only be "old used guns".