the cast of black lighting said that they would love to do cross over with Super Girl or the flash

No, nor do I think it would happen. As has already been said, the only thing linking BL to the other Berlanti shows is the Berlanti name.

I'd be okay with this, but IF it happens, it won't be until next season. I get the minor suspicion that Black Lightning takes plac on Earth 38. Meta-Humans weren't known, by the media, until the Particle Accelerator explosion, on Earths 1 and 2. That was roughly 4 years ago. But Black Lightning "retired" 9 years ago, and the media knew about him.

Furthermore, the news report on Black Lightning mentioned something about super powered heroes in other cities. This could allude to Supergirl/Superman and more.

Or they could be on their own Earth. It's all speculation, at this point.

If they were planning on having Black Lightning happen on the same Earth as Supergirl, then they definitely would have alluded to that IN Supergirl. Did you see how much they were marketing BL this past month? They would've wanted any cross promotion they could get to make sure the show is successful. There probably would've been events similar to when Barry Allen appeared of Arrow before The Flash started.
However, I still love the idea of them crossing over with Supergirl or any DC show at some point.

I was thinking about that as well, but what earth are they on and how would they figure out that he even exists?

I hope not. Other than the Berlanti production name, BL has it's own creative team that doesn't involve the Arrowverse team, except for the superstar Blake Neely for the music. I think.

It has a completely different tone. It's dark, gritty, way more adult, the hero chooses to kill when all else fails. In the short space of the Pilot, the characters are 3 dimensional right out of the gate, and not necessarily likable, but interesting. It has more in common with a Netflix series except for the lower budget efx. It screens as an actual drama based on a character with unusual powers rather than a comicbook fantasy.

It was a fantastic Pilot and I wasn't bored for second. I really hope it wasn't a fluke and the rest of the season is as good as the Pilot.

I'm not dissing the Arrowverse by any means. I'm just saying it's a different animal. It's quite refreshing to see the CW branch into a different style of storytelling.

I'd be okay with this, but IF it happens, it won't be until next season. I get the minor suspicion that Black Lightning takes place on Earth 38. Meta-Humans weren't known, by the media, until the Particle Accelerator explosion, on Earths 1 and 2. That was roughly 4 years ago. But Black Lightning "retired" 9 years ago, and the media knew about him.

Furthermore, the news report on Black Lightning mentioned something about super powered heroes in other cities. This could allude to Supergirl/Superman and more.

Or they could be on their own Earth. It's all speculation, at this point.

Hmmm Speed Force Lightning versus Black Lightning?

Or Livewire Team up/fight with Black Lighting?