Frontpage pagination by week

Use the page number to calculate a new date to get the week to fetch:

$page = ( get_query_var( 'paged' ) ) ? get_query_var( 'paged' ) : 1;
$date_to_fetch = time() - ( 604800 * ( $page - 1 ) ) );
$query_string = array(
    'post_type' => 'post',
    'date_query' => array(
        array(
            'year' => date( 'o', $date_to_fetch ),
            'week' => date( 'W', $date_to_fetch ),
        ),
    ),
    'post_status' => 'publish'
);
query_posts($query_string);

If you are working with date( 'W' ), you should always be working with date( 'o' ) instead of date( 'Y' ), because at the beginning of a year it is possible that you are still in a week which is accounted to the past year. For this see the documentation of the date function: http://php.net/manual/de/function.date.php