I think we'll definitely find out who chuck's parents are, both mother AND father. š I think maybe Bart knew that chuck isn't his son, so he Despised chuck. I think that maybe Bart couldn't father a child and so he asked jack for help, maybe this pushed jack and Elizabeth close and they fell in love. That's how he hated chuck cause it was cause of his existence that his wife/gf/whatever she was at that point in time, fell in love with his brother. Cause when they introduced her for the first time, they did show that they were in love and broke apart after the hotel passing around fiasco.
And as for the biggest surprise of the year, my guess is as good as anyone's!!!