I believe Cesc deserves to stay and get more time. I really don't think he's as bad as many here make him out to be. Yes, he has fallen off during the 2nd half of each season he's played with us, but there are also other factors going into that such as being played out of position, collective team failure/collapse, etc. Perhaps there is a mental block component to that now after 3 seasons, but I'm hopeful he can overcome that.
Although he has mostly performed exceptionally against "smaller" teams, La Liga is still a very important competition, and Cesc has played a big part in helping us out grind out those Liga wins even when Xavi and Iniesta were underwhelming at times. No matter the fact that he hasn't performed as well in big games overall, the fact that he consistently been in the top 2-3 assisters and scorers on the team all seasons he's been with us has to say something. Also, most of the times he does play against big teams, he is playing alongside 3 other midfielders or as a false 9.
Point being - I think to say Cesc is trash or not capable of contributing positively to Barcelona is just false. True, he does not have the absolute midfield control and command of Xavi (no one does), nor the finesse and speed that Iniesta has, but he is still a world class midfielder with his own set of positive attributes he brings to the table when he is on top form, which are invaluable. If we can't get someone equal to or better than Fabregas, then I think we should keep him and continuing trying to get the best out of him.
I hope that Cesc stays and that Lucho puts his confidence. Our entire attacking play needs revamping, and I believe Lucho will be great at helping bring that back. If we have our strikers making aggressive runs behind the defense and more dynamic, intelligent combos up front, then Cesc's natural abilities will be able to fully shine and he will be able to thread those through balls and get into those shooting positions that he is great at doing.
He really does seem to have his heart at Barca. I'd be sad if he left, and I really don't know if we'd be able to get another world class midfield that is at least equal to or greater than him. Then again, he has been underwhelming on the big stage for some consistent time now, so I can understand the "hate", but if we can't get anyone truly world class and better, I think we can still dig more out of him.