I believe they'll be available in a future season. This was mentioned in a twab or release update. I'm somewhat not thrilled as I invested a lot of time in getting all exotics and catalysts in season of arrivals (only was missing Mida...did all the raids and heroic missions ones)... But...I had lots of fun doing it, racked up some prestige levi clears in the process and got full armor sets from all of the raids... I for one am fine with letting the weapons out. I hope there's some effort at least needed to earn them but it's whatever... But when these new lights get their hands on Sleeper and it's catalyst, they won't have the same meaning and attachment to these as I do... I'm fine with it. To me, these would some of the featured items in a trophy room if that was a thing... To others, just another exotic... They'll never have what I have as I earned (ground my arse off in prestige, SOTP, etc) these the old way!