I don't even consider Joel an anti-hero for his actions at the end. Put simply, the world isn't really worth saving. The most horrific and dystopic aspects of the world have nothing to do with the infected, per se, but rather with what the struggle for survival has done to humanity itself. I don't get the sense that some vaccine would instantly restore a stable functioning society after 20 years of complete social breakdown. So while I'm sure that Joel hasn't told himself this yet, I don't think that humanity can be saved until Joel and Ellie can help each other learn to be human again. Joel sacrifices human-kind for his own humanity (and the game strongly suggests that Ellie knows this and chooses to accept the lie on the same terms). That's what makes the ending moving, IMO.
Taking the creators at their word, I agree that Joel and Ellie's journey should be over. That doesn't mean that Ellie herself couldn't be the heroine of a sequel. If fast forward 7-10 years, Ellie is in her 20s and Joel is in 60s in a world where aging probably wouldn't be that graceful. It could be Ellie mission, only after having spent her teens in a loving, supportive community, to then complete her hero's journey.