[Bob Broberg SPF667 460BB]

Mikie, Here is the official response:
Q. WHEN THE NEW CROSSING IS BUILT, WILL THE EXISTING ROADWAY ON THE DAM REMAIN OPEN FOR PUBLIC TRAFFIC?
A. The present roadway will remain open to Hoover Dam visitors. However, through traffic and truck traffic will not be permitted on the dam.

I read that as a no.

AZ Bob