Before today it has been pure speculation that this removal of loot would or would not happen. The only time that the WoW Insider staff can think of this happening before (save for the holiday and special events) is with a few old mount models getting changed. And that is nothing compared to entire loot tables being removed from the game. Note that the changes in patch 2.3 to old world loot were just that – changes, not removal.
In many ways this removal does make since, given that the armor models will be reused in Wrath of the Lich King's version of Naxx. While there is similar looking and colored gear floating around WoW, none of it is really twenty levels apart and powerful each in their own right.
However with that said, the removal of items from the game like this stirs a mixed reaction in me.
Part of me doesn't really care, given that it's not going to be useful for my characters past level 68 or so. But another part of me is unsettled that I won't be able to get my lowbie characters a super-powered item from Naxx. Don't doubt that this hasn't been done – I've taken a level 59 toon into MC and retrieved some pieces of gear that've lasted me until 63, and have done the same with Naxx.
The other thing that this removal of loot might do is create the ultimate status icon – old world Tier 3 armor. If people are no longer able to get it, the demand for the armor will be ridiculously high given the non-existent supply. This creates a situation where those who have it still will automatically posses one helluva status symbol, especially in the years following the release of WotLK.
What are your opinions on the removal of Tier 3 loot? Quite an interesting change, is it not?