If the 2.0 weapons continue to be upgraded post 3.0 then that is an entirely different story (one that justifies nerfs). However, if everyone is back to square one (new relics) post 3.0 - then that in itself eliminates the reasoning behind nerfing the zodiac quests (new players will be caught-up when the new questline is introduced).
At least allow the players who put in the time to have the benefit of glamours. There are plenty of players who suffered through the atma phase (many spent 100+ hours). If these weapons are going to be outdated in a mere 6 months - then what is the point of playing catch-up? What is the point of ever playing at more than a casual pace if all items (regardless of necessity) are gift-wrapped to the entire community? This is an instance where it is not necessary (assuming new relics in 3.0).
Old content should be nerfed when new / casual players are faced with unreasonable amount of catch-up. That I completely understand. If there are new relics in 3.0 - any nerfs lose their purpose.