I didn't bring up Avatar for Saldana because it also was released in 2009. December 18th to be exact. By the time Star Trek 09 was in theaters, Avatar was in post-production. Her contributions had already been added before ST09 debuted.
I'm not seeing your point? The audience already had seen Trek '09 when Avatar premiered, so, they could decide to see the movie or not knowing "Uhura" was in it. Are you saying if Avatar was made a little later they would've chosen someone else to play Zoe Saldana's part?
And what about Kirk's daddy Chris Hemsworth? He went to star in Thor, and in Avengers. Was his part in Trek '09 too small for his future career to be doomed? Additionally, a Horror movie (Cabin in the Woods) Chris Hemsworth made before any of those was released after Star Trek and Thor that doubled it's budget in Box Office, likely helped by Chris Hemsworth's roles in Trek '09 and Thor
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?