I would keep Plouffe. Everyone thinks Sano will be a great major league hitter but until he proves that we need to keep Plouffe. There are still questions about Sano being able to play 3B in the majors. If ALL our prospects make it I could still see a role for Plouffe as a possible platoon partner with Arcia, bench bat, fill in for Mauer when he misses his 40 games, may even be a late inning defensive replacement for Sano.