Was always going to be this way entirely so Arsenal can absolve themselves and make Sanchez into the villain for it all. He'll have to force his way and, honestly, I don't see any other way around it.
Sanchez isn't going to sit on his hands for another year, in a club he clearly isn't committed to, only to get a less lucrative contract with the club of his choice in 2018. Throw in Alexis' ambition and suddenly a Europa League club who aren't going to be realistically challenging for the PL isn't going to cut it anymore.
Then, on Arsenal's end, keeping a ticking time bomb like Sanchez for a year and pissing £50m up the wall is unthinkable. Wenger would do it, I'm sure. Kroenke? Not a chance. And Gazidis is too much of a pussy to go against the owner/board who are the real power behind the business.
Short of a surprise extension, Sanchez walks this year and it's all a matter of seeing it out patiently.