I think they should add an item to each new raid (hard mode) that allows for upgrades to items from the previous raid. i.e.: Hard Crota drops an item that allows VoG items up to the new maximum. HoW hard raid boss would drop an item that functions for VoG and CE items. The gunsmith could be the one who makes it happen, just like Xur's upgrade system. This would keep all raids relevant :) not to mention give our armor some variety if they extended this system to faction armor.