Diaby: Wont be leaving, but considering his latest injury its about time we found a replacement for him because I cant see him doing much for us. I doubt he will be leaving before the end of his contract (Wenger is a fair manager when it comes to players and will only release them in extreme circumstances) so his wages will not be freed up for us to buy someone else.
Chamakh: Hopefully will be on his way but I rate a move 50/50. He has not done anything since his first 5 months with us. He has not really benefited WH. So realistically who wants him? The only hope we have of him going is if we get an offer from where we found him (League or team) and we would not get very much money for him 4-5 mill tops.
Szczeny: Sorry to burst your bubble but I cant see him leaving. Logically we should keep him. Flappy and Mannone should leave before he does. Szczsney is only 22 and would have been rated as a good up and coming keeper 10/20 years ago. Patience has been lost amongst fans in recent decades. If we get a new keeper they should be providing competition for Szczesny not as a replacement. I think that will happen.
Sagna: Last year of contract. Talks have stalled. Two broken legs in the space of two seasons. we HAVE to sell him no matter what price. he has been great for us at times but not this season. I would like to see Bellerin get a chance in his place but that might be asking too much too soon. Any replacement I think should have Premier league experience though.
Gervinho: another 50/50 leaver. There has been talk that some team is interested in buying him for 12 mill!!?? That would be too good to be true. I think he is a decent squad player but Far too inconsistent. I wouldnt mind him staying but if we get an offer he should move on. Replacement wise we should be looking at a WINGER not a flexible forward.
Rosicky: He signed a new contract last summer. Being over 30 and knowing wenger it is likely to be a 1 year contract, yet we have not heard anything about his contract situ since, which makes me think perhaps he got given a 2 year contract. I think he should stay. He is a very good squad player when fit. And can be valuable when needed. He should stay even if he is behind numerous others in the pecking order. His experience and ability are important for depth.
Considering your list I think there is a different list of players that we need to get rid of over and above those you mentioned. That list does include Chamakh and possibly Gerv but more importantly includes: Denilson, Djourou, Flappy, Bendtner, Park Arshavin, Squillaci and maybe Mannone.
Guarantees: Squillaci and Arshavin Their contracts are up in the summer.
Likely: Denilson, Djourou and Sagna.
The others we can only hope and pray they get interest from elsewhere otherwise we are stuck with em.