Aye I'm pretty confident Demba won't be going anywhere for a while. He seems happy here, is under contract for another 2 and a half years, and things are generally going well.
On current form he must be worth at least £20mil, and it wouldn't be worth our while to sell him for any less than that. However, I doubt anyone will stump up that much for him on account of his gammy knee. Clubs were reluctant to take a chance on him as a free transfer in the summer; it's hardly likely they'll be queuing up 6 months later to buy him for £10mil+.