> Is it possible that one day a dinosaur extinction size asteroid will be annouced on a collision course?

Yes, but it gets less likely as we keep searching more of the sky.

You can never _really_ say it's impossible, there can always be a cosmic bullseye heading our way from way off in interstellar space that we can't see until it gets closer.

But there is still room for quite a few rocks in the solar system to have our name on them too, last I checked.