Depends on who the final villain is...
BB, there's no assurance but if there's someone that Luffy will kill it's him due to his deep grudge...
Akainu, death is imminent likely at the hands of Sabo...
Im, we don't even know the motivations and means of that person so it's less likely...
But in shonen stories like OP wherein death rarely occurs esp. in villains, very powerful villains with firm intentions opposed by MCs have high chance to die...