I seriously doubt Obama will chose Biden.
First, he comes off as a pretty nasty guy, which isn't the kind of personality that has attracted voters to Obama. Second, he's run for the Dem presidential nomination twice (1987 and 2008), and his campaign fairly quickly crashed and burned. Since he hasn't managed to generate a lot of enthusiasm from his own party, he's unlikely to do so now. Third, in 2004, he recommended to Kerry that Kerry should pick McCain as his running mate. That endorsement from Biden is not a positive factor for either Obama or Biden.
I, too, am guessing the "Congressman from Texas" will get the nod.