Berlanti is referring to the fact that while the Black Lightning series is in development, Fox has only committed to a pilot order.
That said, DC Comics fans would likely enjoy seeing Black Lightning team up with Arrow, The Flash, Supergirl and the Legends team. It doesn’t seem out of the realm of possibility – though the cross-network crossover would be more difficult between The CW and Fox than The CW and CBS – but depends upon Black Lightning receiving an official series order.
Still, if the tone of Black Lightning is too different from the Arrowverse, perhaps it’s best for the properties to remain as separate entities.
We’ll keep you updated on Black Lightning as development continues.