the people over at sosh put up Grandersons hit chart from comerica last year, and showed where the hits would land at yankee stadium. there was 1 foul, 5 fly outs, and 5 doubles that were easy homers at yankee stadium (and that is just accounting for size, not the wind). that puts Granderson at 41 homers.
if he stays healthy, it isnt a stretch to assume he hits 40+ next year.