Well it could be so. But, as one physicist once remarked, there are hypotheses and hypotheses. He mentioned that all this is like writing fiction . It can become a theory only when it explains all things known and makes predictions about things unknown which can be verified.

Personally, to me the universe is everything i.e. all inclusive. So if there is another universe, it contradicts my understanding. I would prefer terms like galaxies, clusters, superclusters etc. for those 'universes'

This is like they once defined atom as the smallest indivisble unit of matter. Then came the electron proton and neutron but they continued calling it an atom and claimed it is divisible! This contradicts the original definition of the atom