He's a true leader, but if this is really true then it isn't exactly a bad thing, we are selling an old dog for some transfer funds as well decreasing the wage for transfers as well, and Puyols must be pretty high too.
It would be a very bad choice for several reasons. One of the main ones and most important one is that you just can't replace the figure that is Puyol and all he symbolizes on the pitch from one day to another. This should happen gradually. We all know how important he still is during the biggest matches and his absence, not always due to solely footballing reasons, is felt hugely and has largely a negative impact. This years Cl-semifinal, regardless of Bayern being the superior team this year, would not have ended like that had Puyol played both games IMO.
Moreover the club is undergoing a transitional period. For that Puyol will be needed alone.
Also we would not gain anything financially from selling him. His contract expires in 2014, If I remember correctly, so he will basically leave for free.