The real question is, is now that Saturn and Kuma are there, what is Kizaru going to do? When he arrived on the Island alone, it afforded him the opportunity to be able to defeat Sentomaru, while leaving him alive, but with heavy injuries.
His mission was to kill Vegapunk, which he had resolved himself to do, although they have a friendship between them. That's a heavy burden that he was willing to bear. But now that Saturn is there, he's not going to let Vegapunk, Bonney, or Kuma escape alive. Will Kizaru watch and/or participate in the killing of all three of them?
Kizaru is witnessing the truth of everything right now, alongside everyone else. Saturn experimented on Bonney, killed her mother, and turned her father (His friend) into a mindless machine. Will Kizaru's justice allow him to sit back and let Saturn kill three of his friends, with one of them being a 12 year old girl? Is he that kind of a monster?
We will find soon enough.