SETI is one of the few things out there that comes close to 'pure' research. Since they don't know what they are looking for, it is impossible to predict what they might find.
Sure they know what they are looking for: signals that show evidence of being intelligently designed. (Don't tell the evolutionary biologists.)
(Incidentally before the defenders of neo-Darwinism jump on this: ID as proposed is not a scientific theory, as the attempts to make it falsifiable are based on a priori probability estimates that are neither falsifiable nor verifiable. I just have an objection, on behalf of archaeologists and SETI to the notion that intelligent causation cannot be regarded as a cause in a scientific theory.)