I was thinking it could only be a voice cameo, as The Clone Wars established Qui-gon only appears as a Force ghost on Mortis. Other than that, he’s a classic disembodied voice, and I don’t mind that at all. It would contribute to the sense of Ben’s isolation if his only company is a voice with no body he hears in his head.
As for the overall plot of this show, I’m betting someone (possibly Moses Ingram’s character - she mentioned something about ‘playing with lightsabers’ on her instagram earlier, although it might be nothing it could mean she’s an Imperial Inquisitor) will find out about Luke, and Obi-wan will have to pursue them. That’s the only way he’d leave the planet and potentially come into contact with Vader.
I still have massive reservations about this ‘rematch’ they’re teasing, but I think I’m beginning the period of slow acceptance. I want to be excited for this show, I just need to hear more about what direction it’s taking. It has the potential to make the original trilogy and Obi-wan’s story more compelling, but it also has the potential to fuck everything up.