A Goodreads user asked:
What do you think would happen if Firestar DIDN'T die?
Liam If Firestar didn't die, he probably would've died soon anyway. Also if Firestar didn't die Brambleclaw wouldn't have become ThunderClan's leader and he wouldn't have picked Squirrelflight to be his deputy.
Emma Flowska™ It would be almost to perfect. Firestar would go on and just die a different. I'm pretty sure he wouldn't live very long after the battle. (Remember he died of wounds, not the tree. Dovewing only saw the tree fall, but never really saw Firestar under it.)