The idea of this local universe being part of a multiverse would not be too surprising and would have analogy to before and after we discovered galaxies. My understanding is that big bang (inflation theory) actually was just significantly supported by WMAP data. I think BB theory has held up quite well, and will probably be supplanted by a more detailed and comrehensive theory at some point, like Newtonian gravity being absorbed into relativity theory. However, so far I see nothing in regards to dark matter and energy or other issues that makes me think that the big bang theory fails to explain what we see within our current understandings of the phsical local universe.

I always go back to the Shakespearean quote, "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy." whenever someone starts to think they have a comprehensive theory. All we can do, is plod along. As our tools get better to explore and plumb the depths and breadths of the universe, we should be prepared to come up with new theories and understandings to fit our new discoveries. In other words, business as usual.