The fans may not like it but whispers have been made that he could return, one day. He gets on with Wenger but wants a competitive team (who pay good wages too obviously). Arsenal with a bid of say 18m may get him and he'd instantly improve them. Cazorla is his replacement but they are always short of alternatives as Rosisky is injury prone and so too Wilshere in the other CM position.
They have a first choice of Diaby, Wilshere and Cazorla on quality. 2 of the 3 are injury prone. Then you have Ramsey (not all that) and Arteta (same as Ramsey and also ageing, does a job at CDM but not ideal player there). Nasri instantly improves all situations.