Megaverse

Several of the more interesting variants of string theory propose that our entire universe is one simple three-dimensional membrane existing within a higher-order bulk universe, or megaverse.

An important part of Susskind's picture is that each of the pocket universes is expanding like a bubble, so you can't get out of one, but the whole megaverse also expands, so the bubbles don't collide.

As there is no evidence of an unconditional singularity anywhere it is highly likely that there are other universes and even “mother” megaverses of infinite proportions.