I still reckon he might stay. The last words from Cesc himself were "I'm happy at Arsenal and in no hurry to leave". Everything else is all speculation in the newspapers with absolutely nothing from either Cesc or Wenger.
Even if the rumours of him since changing his mind and wanting to leave are true, there's still the rather big issue of the fee. Barca have, at present, not even made a bid, but are apparently thinking of bidding around £30 million.
Arsenal, on the other hand, are under no financial pressure to sell (they're almost debt-free now), have no desire to sell and have a player on a five year contract. Even if he wants to go, United showed how a player can be made to stay if the bid isn't big enough with Ronaldo. Real offered a fee in the region of £50-60 million the year before, and United told them to get lost. He stayed another year, they did well, Real offered £80 million and off he went.
I suspect the same may happen with Cesc as Arsenal want at least £50 million. There's a rather large gap between £30 million and £50 million and Barca have already dropped the best part of £40 million on Villa. If he's worth that then Cesc, five years younger, is worth at least £50 million (especially if City are willing to pay £25 million for Milner). Are Barca willing to pay £50 million for one of their own youth products? I'm not sure they are.
Either way, I just wish it were sorted. If he goes, he goes, but we need to look at who we're bringing in.