Hero Character?

I have mixed feelings about the death knight hero class supposedly being introduced in the supposed upcoming expansion, Wrath of the Lich King. My main concern is the mechanic for obtaining the death knight. Apparently you meet certain criteria and can unlock the class for play, which will begin at "a high experience level," meaning it's already got a bunch of levels.

On one hand, thank God that if I roll a death knight alt, I don't have to set foot in Northshire Abbey or the Barrens. But...my concern is that hero classes would then replace the base classes under this mechanic. I love my lock. I want to take him all the way to 80, or 10000, or however high they'll let me go. But, if the hero classes end up being more powerful, will I have to abandon my main to see all the content?

I'm betting they'll be balanced against the other classes and that you'll just be able to make them after you meet the criteria...I hope....