Elder Spock tells young Spock, ‘I couldn’t tell you the truth about what’s happening, because if I had, I would have robbed you of the benefit of realizing the greatness that you and Kirk will achieve together — and the amazing friendship that you’ll have. You had to discover that for yourself, and I couldn’t get in the way of that. And in our original version, younger Spock says, ‘I’m still not sold.’ Elder Spock said, ‘Well, don’t take my word for it,’ and he handed him a little disc — a DVD, really — that projected a hologram, and then he walked away. And the hologram was of Kirk. It would’ve been Shatner.
Shatner’s voice-over would then play over the final minutes of the film. They ultimately weren’t convinced it was worth it to go ahead with the scene so they scrapped it. Read more about what they had to say over HERE.