I personally don’t see an immediate viability for a 777 Freighter. The reason being is that you still have the 747-400F, now in an improved -ER configuration. Especially when you consider that the 747 was purposely designed to be a freighter with its raised deck and upward swinging nose door, it allows for larger container types to be loaded from the front that other freighters can’t take in the side door. With this available, there’s no way Boeing is going to bother developing a 777F to compete with one of its own products. Now if there is some aftermarket company that potentially con convert pax 777 into freighters, that’s a whole different argument.