While this reading may at first seem possible, a number of observations, in my opinion, render such an approach highly implausible. In sum, I would suggest that while Gundry’s reading is possible, it is exceedingly unlikely. Indeed, I think a growing number of commentators would agree--even Protestant ones.
First, we must first acknowledge that it would be odd for Jesus to state that he was building upon a πέτρος (petros), since one would usually associate a building-project with the more sturdy foundation of a πέτρα (petra), as Jesus’ words in Matthew 7:24 indicate.
Going on from this we can point out that, as reader Cale Clark wrote correctly in the comment-box of the previous post, there is a perfectly natural explanation for the πέτρος (petros) / πέτρα (petra) construction: πέτρα (petra) is a feminine word. Jesus could hardly have used a feminine noun as the name of Simon Peter—“You are Petrina”? I think not!
So, grammatically, we have a problem. On the one hand, one cannot use πέτρος (petros) to describe a suitable foundation for a building project—for that, again as Matthew 7:24 indicates, one must speak of πέτρα (petra). Yet, on the other hand, Jesus can hardly name Peter, πέτρα (petra)—because the word is feminine! Jesus can’t give Peter a feminine name!
In fact, if Jesus wanted to apply the terminology of the πέτρα (petra), i.e., that which the Church is built upon, to Peter, we would expect to find very kind of shift in language we have in Matthew 16:18. France puts it well:
“The reason for the different Greek form is simply that Peter, as a man, needs a masculine name, and so the form Petros has been coined. But the flow of the sentence makes it clear that the wordplay is intended to identify Peter as the rock.”