I mean that weapons like FB, VoC, Black hammer, etc. All the endgame weapons and armor will never drop again. EVER. When year two begins, and when a player buys TTK, all the year one endgame weapons and armor will never drop again. Meaning all year one weapons are absolutely unattainable. They will be replaced, by a new set of weapons and armor for year two. Not like a 2.0 version, but a completely new look, appearance, name and stats for each armor piece and weapon for year 2 gear that replaced year ones gear.

That already happens with the standard gear you can buy from the vendors. As far as raid gear sets go, that is doubtful. Older raids have never dropped newer content, ever. You can't get something like nothing manacles or dragon's breath in VOG. Also making Blackhammer never drop again defeats the point of nerfing it. All the Y1 raid sets are still going to drop but now they're going to be irrelevant to the endgame.

But it would greatly motivate players to get the new versions. I'm not saying just the raids, I mean EVERYTHING. PoE, ToO, every year one weapon and armor piece replaced and gone. The tower does it every DLC. But this is the beginning of a new year, and Bungie seems to be adding, improving, and fixing many things in Destiny now. They're reorganizing the story missions, replacing the ghost, adding many improvements to the tower, fixing many of the glitches, attempting to balance the weapons....again, not to mention the giant DLC. Also, the weapon nerfs for black hammer and Gjhallerhorn will still be relevant for the year one content, so technically if they do replace all the year one gear, the guns should still be as good, aside from the weapon nerfs. It's just that the year two versions will be better. I think.

I Very much doubt that bungie will simply switch out the old drops in the raids for new content, they have never done this before and even stated that much when new expansions were released. Secondly, nerfing specific weapons like BH or GHorn doesn't make sense if they were guns that no-one can obtain anymore. Balancing is made in the mind of what MOST players are using, not the least. Making it never drop again is a sure fire way to make it rare to the point where that gun is irrelevant in terms of balancing.