Suarez's development has only stalled because our U21 system has been a graveyard for young talent, ruining potential. He has remained a regular for Spain at every youth level and one good loan move could easily have the Guidetti effect on him. Selling him would be stupid, although we may not have any choice in the end if he wants to go, due to his apparent contract situation. Make no mistake, Suarez is a top young talent that most clubs would want, and has the potential to be a top level player (he is still a teenager remember). That Barca are willing to pay cash for him with a year left on his contract is the giveaway.
Hopefully the club can convince him to stay with a wage rise. 4 million euros is peanuts and not much more than the £2.75m his original transfer fee can rise to (several of the bonuses that could see that transfer fee reach £2.75m have probably already been triggered, such as first team appearance).
PS: If Barca do get him it'll be the next strike in the Rosell vs. Soriano war and I hope we retaliate.