Lost content?

In a recent comment here, Shalkis remarked that the Burning Crusade expansion would make a lot of the existing level 60 content useless. Hellfire Rampart is not harder to beat than lets say Scholomance, you could even say it's easier, because the dungeon is shorter. But the loot in the new dungeons is significantly better than the loot in the old dungeons. So except for special tradeskill items, like righteous orbs or dark runes, there is no reason to visit the old level 60 dungeons any more.

Now veteran players won't mind. We visited Scholomance a hundred times and won't be sorry to never see it again. But new players join World of Warcraft every day, and there will be people reaching level 60 for the first time only after the expansion has come out. And they will quickly realize that the Outland dungeons are significantly more profitable than the old world dungeons.

Similar things hold true for some other level 60 activities. PvP won't really be affected, as you can use the honor points and victory marks you earn at level 60 to buy level 70 gear. But who would for example do the incredibly difficult tier 0.5 upgrade quest when he can do simple level 60 quests in Hellfire Peninsula which give much better green gear as rewards? And if you can level up further, why would you want to spend a lot of time grinding faction, for example doing the field duty quests in Silithus?

So what do you think? Will there be a big part of the previous level 60 content unused after the expansion comes out?