The problem here is this: (Your comments in blue)
I'm surprised that so many of you interpret it this way, that Jesus was merely stating the possibility of John being kept alive until His second coming.
So many believe this because we believe the Scripture evidence. It is what the Scripture says. It is the grammatically correct way to understand these verses and understanding the words, as written in the Kione Greek, is how one comes to the Truth - with the assistance of the Holy Spirit who guides us into that Truth. One can also come to the Truth with a good translation but it is still better to work in the language of the original autographs.
You have the right to your own opinions, but I think you're reading into the whole use of the word "if" too much.
My opinion is irrelevant - if not based on the proper Grammar and Hermeneutics and thus, provable by Scripture.
To me, Jesus told Peter in plain language what he was going to do with John because He loved him so much
And here is the problem - You said "To me"... If one is not willing to conform their understanding of the Truth when presented with the evidence - Then that one is not teachable and will most likely be susceptible to many false doctrines.