I was personally raised believing that Matthew 16:27 speaks of the “end of the world” while v. 28 foretold the day of Pentecost, only a few months removed from when Jesus spoke the prediction.
This is the popular view in the amillennial world. The dispensationalists insert a 1000 year gap between the verses.
However, this position is simply not contextual. It is false. Verse 27 says what Jesus was going to do; v. 28 tells us when he was going to do it. There is no gap between the verses!
I just posted a new video demonstrating this, with an examination of the Greek grammar. Check it out!