In all likelyhood, probably not but there is still the fact that we cannot see the Alpha Centauri system in detail with modern telescopes, so there is still a small chance of it actually existing.
However, while the chances of an exact Pandora replica being unlikely, there is a decent chance of a planet other than Earth supporting life. As far as we know, there could be literally anything out there, we just have to go looking for it.
It is also worth noting that there is a moon called Pandora. It is one of Saturn's moons that lies in the F-ring. It has a very low density and has a very porous, icy, body. It was discovered in 1985. The nearest moon is named Prometheus and they even have an interchangeable orbit with each other. It's nothing like the Pandora in Avatar, it much more closely resembles our own moon.