I don't think you need worry about the 470NE going anyplace soon, if at all. There are many others that are simi popular today that will go away long before the 470NE. The 500/416K is one that I believe will die on the vine long before the 470NE.

Having said that, the 470NE is not my favorite cartridge for dangerous game in a double rifle, but I do have one. I'm not an elephant hunter, but if I were the 500NE would be my first choice for that persuit. IMO, the 500NE is a better elephant cartridge that either the 470NE , or the 577NE. It hits harder than the 470NE, and it pennetrates better than the 577NE.

There is no question that the 500NE packs a bigger punch to the shooter as well over the 470NE, but is less than the 577NE.

My thing is cape buffalo, and the 470NE IMO is not needed for that animal, and for my personal use my favorite double rifle for up to, and including Cape buffalo, is a fine 10 pound or a little less 450/400NE 3". The 450/400NE 3" Is IMO absolutely perfect for cape buffalo, and is far more versitile for the cats as well. With proper loads I don't believe there is a better follow-up rifle that a nice 10 pound 450/400NE 3" double rifle for lion or leopard, and is up to about anything a buffalo has to offer.

The above is only my opinion, and is free for the taking or leaving!