It looks like it's happening now. Sanchez has all the attributes to be a great player for you. He is in his prime, and you can have him for 3-4 good years. He will probably be a succe right away, and that's what you need now.
You need proven quality upfront to catch up with City. Martial and Rashford have great potential, but they can not yet carry the team, when the going gets tough.
It looks like good business the club has made getting him, and also a statement of intent. Getting rid of Mkhitarian as a part of the deal is a win win..
You may call Liverpool a selling club, and you're right.. We couldn't hold on to Torres, Alonso, Suarez, Sterling, Coutinho..
But what does this transfer say about Arsenal right now? Their fans must must be fuming, and rightly so. Arsenals best player in a switch with a reject from Manchester United is hardly what they need, when they should be trying to catch up with you.