I wouldn't expect much to happen, at least not in the short term. I mean if it's *really* bad, sure, that could provoke a crisis, but we're talking "pyromaniac redheaded ghost!" bad. Short of that, I think we'd just see increased polarization of the fan base. The wait for Episode 9 would have more frequent and more caustic arguments than usual. Zoey would probably be the new Maya. And maybe DPC's Patreon numbers would level off (rather than slowly grow), but I think that would be the extent of it. At the end of the day, the Interlude is just a side dish; my guess is most people will wait for the main course before they demand to speak to the chef.
That said, if the Interlude goes over badly it would definitely raise the stakes for Episode 9 (and for Zoey in particular). DPC would need to keep the focus closer to the existing main girls, which in turn could make it harder to get Zoey up to speed. If DPC still manages to deliver, the Interlude's problems should fade into the background. It would be like the poor resolution to the M&J crisis in Episode 4; it's not forgotten, but most people are content not to pick at old wounds. If the problems with the Interlude continue into Episode 9, however, I think that's when you'd start to see people losing interest in the game in large enough numbers to matter. Even then it would be a slow process unless DPC really screws the pooch.
I take your point and generally agree. As much as I'd like new Episodes sooner, I'm okay with DPC taking his time to get them right.