It is a scary thought to think that if we were indeed the only planet in the entire reaches of space that is capable of supporting life as we understand it then we are indeed doomed.. I find that scenario very hard to come to terms with..
Although our initial findings so far point to maybe being alone I would find it hard to believe that we were just a random one off event in all that space... There must be other planets out there that can sustain us or at least have life in some form or another. Depending on the conditions the life would obviously vary. Some planets may be capable of only being able to support the life found on it where we might struggle or even find impossible.. If we could find any evidence from anywhere out there that there may be other life regardless of what type of life it is then there would be hope...
Given the distances required to travel in order to find such places great technological leaps would need to be made in space travel like hyper speed, warp drives etc, It may be some considerable time before any of that becomes a reality and if you think about how far we have managed to go over all those years it's still only baby steps in such vastness that it seems almost impossible to calculate... Space is so big and seemingly endless that it could take hundreds of years before our signals or probes reached something that might be able to respond to it, if at all..
Who knows maybe if we have not received a signal or found a planet capable of life by the time our planets resources have run down or overpopulation renders it uninhabitable we may yet end up cruising through the universe on big ships like Battlestar Galactica hoping to one day find a planet that can support life.. If we are indeed the only form of life then eventually we will die out if the tech does not advance quicker than our ability to consume..