I vote yes.
Here's my argument...
OK, lets use our hobby as an example. Every year, Marine Biologists from around the world are always discovering new species of fish, inverts, etc... in our oceans. What's not to say that the same cannot be true for the earths surface; that other species of animals exist that we are still yet to discover?
Just this year, a frilled-shark was found near the coasts of Japan and filmed swimming in one of their aquariums before dying. This fish was thought to have been long extinct millions of years ago.
Another example is the the Ivory-Billed Woodpecker. For years, scientists thought that this species of bird was extinct. But in 2004, video footage was caught that showed this bird in flight. Additional research conducted by scientists lean towards the possibility that this bird does exist in the eastern Arkansas area. This was all determined by comparing audio recordings of this bird from 1935 to the ones recorded by scientists that they caught during the course of 18,000 hours of audio recordings in the woods of Arkansas.
So in conclusion, I always lean the possibility of Yes, unless scientific evidence conclusively points towards a No. That's my two cents.