We have good idea about the number of planets in the galaxy, and while I cannot remember what that number is, it is pretty large. There is bound to be *some* non-earth planet out there that is in the Goldilocks zone and has all the other ingredients for life. It would be more improbable if there wasn't another earth-like planet than otherwise.
However, I think that this discussion should not focus on life-sustaining planets, but on whether or not civilization could survive long enough to meet ET. In other words, we should be talking about the L part of the Drake equation, or whether species of intelligent life are prone to nuking themselves out of existence. I, personally, am optimistic about this.
Given our current technology and the rate of advancement at which we discover new technology, we should be able to locate other beings that inhabit the universe in the very near future. If not us, it is totally feasible that other beings will make contact with us first, if they haven't already done so, based on UFO sightings.
To think that we are the only living things in infinite space is egotism, to the highest factor. One day, we will make contact with other life forms.
There has to be life on other plants, and it's just a matter of time before we make contact with other beings on other plants. The government needs to reopen our space programs, so we can explore more. Their is a need to explore, so we can find out what is waiting for us.
The odds of us being alone in a universe that is infinitely expanding, infinitely gaining new stars and solar systems, and infinitely gaining new possibly inhabitable bodies is almost infinitely small.