Even with Johnson, it's still possible (maybe 50-60% likely) that the BoSox don't even make the playoffs, making this all null and void.
It's the same if he goes to Anaheim. You'd think the three AL teams he'd go to are the Yankees, Sox, or Twins. The Yankees are a shoe-in and if he goes to the Sox or Twins, he tips the scales in that teams favor for a virtual play-off lock.
Anaheim and Boston both seem like a risk for not even making the playoffs.