Fabregas' future depends on many things. I think he realises his importance for Arsenal, he is the captain of the team and if he gets a taste of silverware this season, as captain, he can become more bonded to the club.
But there's also the World Cup, his success with Spain could change things. We cannot know for sure. I hope he stays of course!
About Barcelona selling Messi: this would never happen. Not even for 100 million or 150 million (I could see Barca snubbing an offer like that). He's a 22 year old genius ready to take over the world. And I think he wants to stay put.
Speaking of the devil, the Barcelona game seems out of hand now... Before sales opened for Red members it is sold out already!! WTF!