True, whenever we speak about future under these terms, we do so under the limitations of our current technology and physics¡ knowledge. Lightspeed is our limit (as far as we know), and we haven't been able to even reach that.

The rest, is suppositions fed by people spreading "news" that have no real hard evidence behind.

Your reference to ball lightning (how casual, I lived in the Andes for several years) being confused as "alien vehicles" is a common misconception. Some believe they are "la luz mala" https://es.wikipedia.org/wiki/Luz_mala
Others, aliens.

It is just lightning, until proven differently.

It is also true that we are a bellicose civilization, and that we've no way of knowing if any "visitors" didn't actually evolve over a warfare-based culture and expansion. I always considered that we need to be very cautious whenever we "call to the stars"... We never know what we could we be inviting into our primitive civilization.
In case we contact a Civ that is rather equal in technology to us we've nothing to worry about. But, if they're more advanced... we may be fucked!