John 15:16 is referring to Jesusâ 11 faithful apostles whom He Himself hand picked. The context does not support anyone outside of the 11 apostles. Revelation 2:20-21 is very clear.
Just as you said the âyouâ is referring to saved people in 2 Peter 3:9 the âyouâ in John 15:16 is referring to His 11 faithful apostles.
Lord Jesus says "you did not choose Me, but I chose you" (John 15:16) and in the same passage the Word of God says "I chose you out of the world" (John 15:19), so the King of Glory is talking about salvation. Lord Jesus says "you" again and again.
According to the Apostle Peter, the context of Lord Jesus' words including "you" covers all believers in all time, per this account:
Cornelius is of crucial import to this topic for among the places that we find fulfillment of the Word of God's promise of the Holy Spirit is when Gentiles at Cornelius' place were filled with the Holy Spirit (Acts 10:44).
At a time after the outpouring of the Holy Spirit during Pentecost (Acts 2:1-4), Peter recounted to the apostles and brethren about the Gentiles Cornelius with his relatives and his close friends, and the account Peter shared of the Gentiles receiving the Holy Spirit with being saved illuminated that not just Jews would be saved but also Gentiles would be saved (Acts 11:1-18).
At that time, Peter said to the apostles and brethren "And I remembered the word of the Lord, how He used to say, 'John baptized with water, but you will be baptized with the Holy Spirit'" (Acts 11:16).
Prior to the time of the outpouring of the Holy Spirit during Pentecost (Acts 2:1-4), Lord Jesus said "John baptized with water, but in a few days you will be baptized with the Holy Spirit" (Acts 1:5) to the apostles whom Jesus gathered togather (Acts 1:4) which included Peter, and Jesus says "you" right here - with the apostles present right there, Jesus says "you".
Later after the outpouring of the Holy Spirit during Pentecost (Acts 2:1-4), Peter remembered Lord Jesus saying "you will be baptized with the Holy Spirit" and there is the word "you" (Acts 11:16) which Peter tied to the Gentiles Cornelius with all his household (Acts 11:14); furthermore, Peter tied when Lord Jesus says "you" to all believers in all time (Acts 11:17)!
Since the Apostle Peter includes all believers in all time when Lord Jesus says "you" as recorded in Scripture, then this results in the Word of God, Lord Jesus "you did not choose Me, but I chose you" (John 15:16) as well as "I chose you out of the world" (John 15:19) binding all believers in all time.
The "you" in John 15:16 applies to all believers in all time.
Man can do nothing at all to be saved, no free will choice, nothing (John 15:16-19).
God is exclusively in control of salvation of man (John 15:16-19).