We will never find a "new Earth" -- there will be too many chemicals, bacteria, viruses that will be deadly for humans.
Stated on what basis? We have zero observations to choose between these possibilities:
1. Life in general is poorly able to attack alien life. Our defences will overwhelm their bacterial attackers and vice versa. The Space-opera writer's choice.
2. The reverse: their bacteria would rapidly reduce our higher life to smelly slime and vice versa, followed by a long battle between two different clades of single-celled life for supremacy or symbiosis.
3. A one-way knock-out victory: our bacteria overwhelm their biosystem in short order, or their bacteria overwhelm ours. There can be only one ....
4. Panspermia: all life in our galaxy has a common origin, so it's only invaders from Andromeda we have to fear.
5. There's only one way to do life with the physics and chemistry of this universe that's not a thermodynamic impossibility, so convergent evolution means it'll look like panspermia even though it isn't.
All of which is ignoring the extreme unlikelyhood of mankind ever reaching another star. We are too fragile and too short-lived to endure interstellar travel at a realistic (small) fraction of the speed of light.
Our Von Neumann machines have a better chance, but the last place in the universe that Silicon-based A-life would want to conquer would be planets with moist oxidizing atmospheres. Alien A-life might even be established in our Solar system, and if they don't use radio to communicate (or if they use VERY efficient coding indistinguishable from noise) we might not have noticed it!