Probably not. It's just a wild guess at this point, but I think the Dems ticket in '08 is probably going to be some variation on Clinton/Obama.
I would be very surprised if Obama is on the ticket in '08--for one thing, he's just a freshman senator, it's way too soon for him (John Edwards, anyone?), and secondly, he'd be considered way too 'threatening' with his "star power" and political ambitiousness.