A friend sent me an article indicating the Thunderbirds will be using the F-16C Block 52 for their 2009 season. The airplanes (I believe the first has been handed over for modification and update) are going through an extensive modification program and won't be ready for the 2008 season.
I got the impression these weren't brand new jets. On the other hand, there was nothing in the article to indicate what unit(s) the planes came from. I'm assuming they'll get a Block 52 F-16D or two as well.
I have to wonder how much difference there will be in the show they perform. As I recall, Block 52 is quite a bit more powerful than the Block 32s they now fly.