Well a loan is better than him rotting on the bench here. Unless he fails big time in Arsenal, his price should stay level (... we dont pay salary) or his goes up. If no other club is willing to buy him for a decent amount 15-25m this window, then go for the loan.
On a personal note: i think he will do good in Arsenal as a squad player on a loan, but it will take years for him - most likely never - to establish him as a starter for the big clubs. But can we sell him for 20m in the summer, i think its a win-win-win for all parties involved. A squadplayer in the range of 15.-17. player in the pecking order, is decent for a player of denis' talent and quality.