That's the point, hopefully the new weapons are freaking amazing so we don't have to use the older weapons. However the option for us is there to use those weapons if any player desires based on the fact that they earned that weapon. Those weapons are apart of their legend as a whole yet I highly doubt the fatebringer would always be the best option and so on with other guns. The hope is with each expansion more and more guns are added to the pool that are just as viable and maybe even more special. This way our time wasn't wasted and there would be in total much more weapon diversity than just each new expansions "best" guns.