Just because a VFX company isn't doing the effects any more doesn't mean the show won't continue, all it means is they aren't using that company any more. They could just be changing companies.Halon. They do previsualisation. All the smaller VFX companies have been released from contract.
The plan when Disney first bought Fox was for Hulu to continue as the streaming service where they put all of their stuff that isn't family friendly. Disney has had other companies that they used for stuff that didn't fit the family friendly image they kept up, and now that they own Fox they have even more of that kind of stuff, so it makes sense they're going to want a place to put it. They're not about the put things like Deadpool, or the Alien and Predator movies on D+.Hulu seems to be killing a lot of its programming. I expect that once Disney buys out Comcast's stake it will probably be folded into Disney+ and anything non-Disney in tone or approach will be cancelled, including The Orville if it survives that long.
I've seen actors with regular roles on one show, pop up in another, so depending on what kind of role it, there's always a chance she could be doing both, or they could be getting rid of her character. Shows often go through a bit of a revamp when they change homes, so I would be surprised if we see some cast changes, or a change in VFX studios.I’d say the new actress that joined the show for Season 3 now auditioning for Silence of the Lambs is evidence enough, and we’ll know in a matter of weeks if she’s cast. That show has at least a 13 episode order. Yes, it’s possible her Orville character is written out of any potential Season 4, or she has a 1 season deal.