Forgive me if it turns out I'm telling you things you already know, but ...
The highway US 61 has a legendary mystique in the folklore of blues, jazz, and rock and roll. That's especially true of the famous "crossroads", the intersection of 61 and 49 in Clarksdale, Mississippi, where the blues artist Robert Johnson according to legend sold his soul to the devil in exchange for his talent. It's not surprising at all that multiple movies would be made dealing with music and myth and highway 61. I'm surpised there haven't been more.
I doubt very seriously that the planned 2008 Highway 61 movie is intended as a direct remake of 1991's Highway 61, since the latter it is a small, obscure, indie film. (I liked it though.)