Chelsea worries me. If Leo is even contemplating the possibility of leaving Barca, Chelsea is the most worrisome team and the most likely to tempt him. Not only is Chelsea a complete and ascending team right now, but Cesc in the picture can have a huge impact with his relationship with Leo and their girlfriends relationship with each other.
I've also little doubt Mourinho would sell his firstborn to get Leo on his team, and with Chelsea's financial power, Adidas pull and possible involvement and the fact Chelsea can just easily sell Hazard to finance part of the fee, yup they definitely worry me.
Though it all falls on Messi in the end. Definitely don't think the dopes running this team could ever justify selling arguably the best player in history unless the player himself wants the transfer. So as long as Messi doesn't push for this, it won't happen.