Yes, the possibility of multiple universes is relatively high. With so much of the lone universe we know to be a mystery, it would not be far fetched to say that there is not another one. It would be relieveing to know that there could be another universe; that there is more for us to learn.
It is my opinion that there most likely are multiple universes. Scientists do not have a complete knowledge of our universe because it is simply too vast to study completely. Therefore it is easier to buy into the belief that there may be more than one universe where ours ends.
There is no way that what we see is all there is. There is so much around us and in space that there are levels of reality we can not see that are also functioning. I do think it is very possible that there are many universes and we are in just one of them.
I do believe there are multiple universes despite what is popularized in science-fiction movies. My rationale is that our universe is still expanding and continuing to accelerate. The only way that it can continue to accelerate, as opposed to slowing down, is for the universe to be attracted by an alternate universe.
The universe is commonly defined as the totality of existence, from one cell animals all the way to other galaxies. Certainly there are other solar systems and other galaxies out in space, but by our definition, the same universe encompasses all of them. If the Universe is the totality of existence, that means there has to be only one.