There will be more BL 460 cards discovered in the future. Early in 2009 I won a 5 card lot of Broad Leaf 350 backs on ebay and 3 of the 5 cards had NOT yet been confirmed.
New to the hobby were Clymer, Fiene and Mitchell with Broad Leaf 350. I know 350s are a good bit more common but that was 3 unknown fronts in 2009. I know of 2 different Broad Leaf finds not counting the 5 350s from ebay this year. There was a find at the Willow Grove show and another in Boston in 2002 - both of these finds had several BL 460s each.
Here is a Joss from the 2002 Boston find.
BroadLeaf460Joss.jpgBroadLeaf460Jossb.jpg