Here's what some grammar books want you to say.
It is I.
It was I.
It has been I.
It will be I.
It will be John and I.
The selected person is I.
The selected person will be I.
The person selected will be I.
The persons selected will be John and I.
Here's what we actually say, most of the time. This form is also accepted by many, many writers of grammar books.
It is me.
It was me.
It has been me.
It will be me.
It will be John and me.
The selected person is me.
The selected person will be me.
The person selected will be me.
The persons selected will be John and me.
CJ