If a item or Triumph is stated to be in a NUMBERED season or event it you will not be able to obtain it unless Bungie just used a event to introduce a exotic like the Thunderlord or the current Arbalest. Black Armoury, Gambit Prime and whatever comes next season are DLC content and will not be removed. So if you want a Black Armoury weapon no problem as long as you obtain it like everyone else did be it today or in 6 months time. PS. This forum page as the name states is for Destiny subjects and your post covers D2 so should have been posted on the #Destiny2 forum page.