Both books are still available used on amazon as far as I know.

Some of the copies cost as little as $30

I was only thinking about this last night...

Contagious arrived at last so I was thinking about hardbacks of Ancestor and Earthcore.I'm gonna go write Crown a nice letter this evening :) 

My guess is that Earthcore and Ancestor won't be printed again until 2010-2011 unless we all write letter to Crown strongly suggesting that they re-release the books.  However, as stated above, you can buy copies on Amazon for around $30.  I would highly suggest that you do that for several reasons

1) the $30 price is one of the lowest I've seen in a while,

2) the ones on Amazon will be the true first printing and thus the books will be more collectible.

3) you'll love the books!!!!

"Well. I'll tell you what. You gonna kick it with me. Or I'm gonna kick you out. What you think of that?" Sister Mary Clarence