I'd say the likeyhood is that this deal will go through. However, i wouldn't say its a certainty just yet, people are using our past dealings saying that we cave in all the time, the only thing i would say is the circumstances are slightly different this time.
Back then, we couldnt really afford to not take the money. We needed to trade players if we wanted to make new signings because the stadium still weighed heavily on us. We couldnt afford to pay the wages you guys were offering, & you guys were selling a vision.
As for Van Persie, what he did with Utd would probably act as a deterrent to Wenger doing the same, rather than seen as a positive thing. That probably hurt him a great deal watching him basically win the league for them.
Now, we aren't under pressure to sell anyone. With the new tv deals & new sponsorship deals, we are a lot more financially secure than we were back then. Add in the fact that the board & Wenger have never been under as much scrutiny, it's a big summer for them, & they need to get it right.
After saying all that though, Wenger usually at somepoint will take into consideration the players wishes. He tends to think of the man, as well as the player, so i think it will all hinge on discussions Wenger will have with the player personally. If Sanchez kicks up a bit of a fuss...ala Van Persie's open letter after his meeting with Wenger, i think he'll probably get his wish. That way it sort of absolves Wenger of the blame & puts the focus on Sanchez himself. If Sanchez accepts that he stays, then i can see Arsenal keeping him regardless if he signs a new contract or not. That way they can think about replacing him next year, rather than have to do too much in one summer.
I will be sad if he goes, but there will be no fume from me. I'll be intrigued to see him at City, & how he fits in. He's indulged at Arsenal to a certain extent, he basically plays when he wants (which is all the time), he is allowed to do what he wants on the pitch, hold on to the ball, lose possession etc as we know he is capable of the spectacular. He is the main man, the focal point of our team, & although he does get frustrated with team mates at times, he seems to enjoy & thrive on that role for club & country. It will be interesting to see how he fits in with what Pep is hoping to do, whether Sanchez has to adapt his game to be a more a team player to do what Pep wants. I think you lose a bit of what Sanchez is all about if that's the case, so i cant see him posting the same numbers as he does for us, but with you guys the responsibilites would be more shared out anyway as you wouldn't have the same reliance on him that we have.