There is a lot of talk about Bayern but I don't see him going there. Reports saying they will make him their top earner. Unlikely IMO, getting Sanchez is not life or death for them. Will they really change their entire wage structure to accommodate Sanchez? I doubt it. Lewandowski and all others will immediately come in and ask for a raise. Lewandowski just blamed his team mates for not getting the golden boat, does anyone really think this is the type of player that will let Sanchez stroll in and be the top earner by far?
Sanchez to Bayern doesn't fit for me in many ways. He is 28 and they would have to break their transfer record for a player that will get for 2-3 years and then will have to replace again, while they currently have the task of replacing Robben and Ribery. It would make much more sense for them to buy a young bright German talent for much less or any other younger talented player from the Bundesliga where they have a lot of draw and bargaining power.
They let a younger Kroos, an immensely talented German that is now one of the best midfielders in the world, go because they didn't want to break their wage structure. Don't see them breaking it for a 28 yr old Sanchez.
As far as when the transfer could be complete, I am expecting sooner rather than later. In comparison with Spurs, Walker could drag on as they already have a very good replacement for him. There would be no point for Arsenal to stall the whole summer and then let Sanchez go on August 28 without getting a replacement. They are probably now working on a few deals like Lacazette for example and once they have that wrapped up, they let Sanchez go, fans go crazy, Lacazette is announced, fans calm down a little, more signings are announced, PL begins, fans are happy with new signings and pretty much all but forgot about Sanchez.