It depends when they do so : if Cortes is killed before the Castillan army supposed to catch him reaches Mexico, Mexicans would still look for the formers a target IMO, and the conquistador's threat would be still a really likely one.
If they do so afterwards, it may be more of a medium-term victory, critically as it would prevent their native foes to see Castillan as that interesting allies. A Conquistador attack is not to be written off, but at least Castillans would be more wary about sending expeditions there that wouldn't be under firm control.
At this point it may as well end as a later Castillan victory (which wouldn't be as easy as IOTL, IMO) up to Mesoamericans being less utterly conquered than being forced in some form of domination : Christianized, "vassalized", in a more diverse (administratively-wise) New Spain.
(Of course, it would have really important consequences on other conquests and expeditions, as in Peru)
EDIT : DIdn't saw the multipe thread crapping the OP did. I fear we may have a troll there.