There is very little that we know about the universe as of now. Even if know it all we will still not be sure if there is more to know or not. Tell me one fundamental field in which no further research is possible? There are no ways we can reach the ultimate truth; with every step taken further we are one step closer but never there. It seems, theoretically only that it will take infinite time to reach the ultimate truth.
Take the example of human understanding over last 500 years. From rejecting the premise of earth being flat, stationary and what not, we have arrived at the level of explaining black holes. Just imagine how one would think when they first found that earth was round and the whole universe was revolving around it. They would perhaps consider it to be the ultimate discovery of all time, but still it was wrong.
There is an inherent nature of this problem that we are right now a part of this system. And to study it accurately we perhaps need to go out of it and see. An ant moving on a ring never realizes if she is moving in a circle (given a large curvature) for her it is just a straight line.
Infinity by its definition is not achievable. Hence a lack of certainty in universe is the only truth.