There's a big thread on this here somewhere. Bottom line is if someone other than Sony produces a DVCPRO HD codec for Vegas, then it will support it. Right now, Sony has placed no priority on creating one themselves.
I did not realize it was that finalized. Wow, that would be a huge mistake. Every filmmaker I know wants either to buy or rent that camera. Conversely, I haven't heard much excitement for HDV at all. Regardless, variable speed 720p and 1080p24 for under 10k (possibly a good bit under if hard drive solutions come to fruition) deserve serious attention.