Well assuming he does come I hope you're right, I will admit that although I watched some of the Juve matches against Barca and Monaco I didn't specifically examine Alves' defensive contribution but much of it appeared to me great team defense and counter attack in a way Pep doesn't really play.
I mean, that would be a concern if he hadn't played for Barcelona just the year before. I think Pep knows what he's getting into with Dani Alves, honestly.
Assuming we get Walker, and I see no reason to doubt we will, I'm not sure there's a better RB in the World you would want to share the time with him than Alves. This signing makes so much sense that even if he did see a decline based on the Prem, which is difficult to imagine.