If you watched the twitch reveal for TTK or vids from other youtubers you might know that (TTK content spoiler ahead) some year 1 exotics won't be upgradable to year 2 exotics. For now at least. More details in this vid https://m.youtube.com/watch?v=RDmX_9cg_rU ( datto's part 2 of TTK infosplosion )There are a few possibilities maybe we will have to fuse some exotics to upgrade them like legendaries which would make TTK even longer and tedious but would make you use different exotics which is what bungie wants. (I think). The second option is that you won't be able to upgrade them at all and you have to use year 2 exotics to deal enough damage. The third one is that you have to re earn them or something which sounds stupid and horrible we all know why. The fourth and last one that i could think of is that that bungie thought of a new way for us to upgrade those exotics but didn't tell us in the twitch stream. If you have any other info please submit them in the comments below.