I realize this topic has been discussed before, but this Yahoo! Sports article - about teams gaming the free agency and Super 2 rules by keeping MLB-ready stars down on the farm - raises it anew. The article doesn't mention Alvarez, and even acknowledges that some comparable players, like Wieters, probably do merit a bit of AAA seasoning, but the general argument is that big-time prospects should be brought north for Opening Day as a matter of course.
My sense of the consensus around here is that, while Pedro will almost surely be ready this year, it's probably true that he will benefit from a couple months in Indy. Certainly, Andrew McCutchen is a strong argument for this approach, as he showed up ready to perform without a hiccup.
Oh, and god help me, hat tip to Bob Smizik.