Now many people are pissed because they think exotics that won't be given year 2 versions will become obsolete. however, I noticed something in the reveal that many may have overlooked.
When DeeJ inspected the year 1 version of LBN and suros regime, at the end, both still had the upgrade bubble(s) which allowed for it to be given a higher defense and attack value, respectively. This is relevant because soon after, the year 2 version of LBN and suros was shown. Now these already had the max defense and attack(280). However, these were missing the bubble(s) which allowed for them to get an even higher stat, meaning they won't go any higher than 280. this means that even though some exotics won't be given a newer version, they can still be upgraded from 160 to 280; they just won't have the updated perks/ looks.
in conclusion, weapons like the gjallarhorn can still remain with you., and be taken up to the new attack cap of 280. they just won't be given updated perks and/or skins.