Ha, he did get back to Gotham from the prison (Africa?) seemingly quite easily, the film doesn't dwell on it much and it doesn't bother me a great deal but it is a valid question.
Bane as a simple henchman was quite disappointing, for me it immediately renders his character and everything he did before as pointless, and any kind of character chemistry with batman also pointless. Is kind of summed up in the film when Catwoman blasts him to a quick undignified death.
I kind of hope it doesn't just get picked up by 'another director for hire' and continued. I think that the only way it can really go is down from here, would Bale do another film, if Blake took on the mantle of batman would it be well-received and would his character have the same gravitas and arc?
Though with the ending as it is I think it's almost set-up for a direct sequel, more so than from the previous film.