On the basis that by "this rock" Jesus means himself and "the gates of Hades" means the power of death, does the "it" at the end of the verse refer to the rock, i.e. to Jesus (rather than to the church)? Both petra and ekklesia are feminine so gender doesn't help and I'm not sure I can trust word order here.
Peter says to Jesus 'Thou art the Christ'.
Jesus says to Peter 'Thou art Peter'.
Peter knows Jesus and names him accordingly. And Jesus Christ knows Peter, personally, by name.
This is the rock - a relationship wherein each one knows the other.
This relationship is based on the fact that they share the same Father :
Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven. Matthew 16:17.
and this relationship is based on personal revelation from that Father.
A rock of a relationship, like no other.
Jesus deliberately names him - first - as Simon, son of Barjona, identifying his natural (flesh and blood) origin. Then he names him Peter, his personal name by which he was known by Jesus and the disciples.
This contrasts the natural origin, from which the revelation did not come and the personal relationship, born of the Father, known of Jesus Christ and his people, from which the revelation did come.
The personal pronoun at the end of the sentence, αυτης, autes, is genitive, singular, feminine (Bagster's Analytical Lexicon). I would say that the word order indicates it referring to the last named referrent, that is to say, the church, εκκλεσια.
The evidence is the word order and that both αυτης and εκκλεσια are in the feminine, singular.
The genitive is used and I would suggest that it is the objective genitive (see Daniel B Wallace Beyond the Basics 1996 p 116) due to the nature of the verb preceding αυτης 'it'.
The verb is 'prevail against' κατισχυσουσιν, katischusousin, and it is as if a preposition were embedded in the word so the genitive is used to express a direct object 'it'.
Usually, one would expect, in Greek, a verb then preposition then a noun often in the genitive case being a prepositional genitive. Here, the language conflates slightly and we have just a verb and a genitive noun.
I cannot personally see that the text is a 'resurrection prediction' as such. It was, of course, necessary for Christ to suffer and die and rise again and ascend in order to build his church. The 'prediction' would therefore have to be understood as the whole work of Christ as prophesied in the Old Testament scriptures and not just one aspect of that whole work, I would suggest.