An intelligent and logical argument, but pure speculation. His statement about the chances of his being correct can only be described as faith. I get why he believes what he believes, but that does not make it any less belief.
Actually, it's not a belief.
It's a "conclusion" based on observation which is subject to change if some event comes along to prove that conclusion wrong.
In a nutshell? That's science.
Observation of what? As Dr. Tyson points out, we have been in the universe for a very short time and restricted to a miniscule part of it. The period of time in which we have been observing much of anything beyond our own atmosphere would, on a universal clock, be counted in small percentages of a millisecond. Yet he says he is 99% certain? I think not. On a universal scale, we have observed almost nothing.
In the absence of evidence, any conclusion is belief. The only evidence presented in that video was that of our own ignorance. I certainly concede that point. But I do not follow how our ignorance is evidence of our knowledge.
We don't only have the ability to observe the present, we can also look into the past (and do so).
But I also agree, 99% certainty is quite a stretch.