The universe is expanding, we detect that the radiation from stars in other galaxies has been stretched out during their transit through space and that stretching is proportional to distance, from that redshift (and the cosmic background microwave radiation) the big bang theory is supported. Given that the evidence points to an accelerating rate of expansion and that the ammount of matter is too little to overcome this and recollapse the universe it follows that eventually it will be spread thin, matter will break down to energy and black holes will evaporate (over massively long time scales). This state of absolute entropy is not going to happen tomorrow.
I think that parallel universes are an interesting proposition, they are introduced as one interpretation of quantum mechanics and also seem to factor into physics hypothesis such as string "theory"; I would not believe in them until a good many qualified people agree on the basis of strong evidence, at the moment it seems a consequence of some of the models and the existence is both untested and apparently untestable.
My understanding is that purgatory is some sort of state ones eternal soul must exist in without any stimulation for crimes against God until you can be let into heaven. I don't have to worry about it because I deny the holy spirit and am going straight to hell without chance of reprieve.