The only thing that I disagree with you there, Cartoon, is Izzy. The only things I can imagine for her are leaving after Owen (probably right before or right after the merge, possibly even earlier), or as an excuse to have an all-girls final two with Bridgette, since they do need to make sure a girl wins.
The same might actually go for Bridgette herself, though: either she gets enough plot to capture the win, or goes early from her team by being charmed by Alejandro.
I also think that unless Gwen really gets involved in a love triangle with Cody and Sierra (which is likely), Heather will make it farther than her, although I doubt either will last long past the merge unless Heather really reforms.
The others I think you're right about: Harold and Leshawna are not going to make it very far, Duncan is almost definitely first out, and Noah won't make the final five but will be close.