Oddly I think a permanent time jump would be a massive cop out. They've established a setting in the 23rd century and I'm enjoying it.
I enjoy it too, but the 23rd Century was only ever going to be a starting point. The original plan was to start in the TOS Era go to the TNG Era and then go to an era beyond that. That was Bryan Fuller's plan. Apparently, they're sticking to this, even if only in broad strokes. Between the Spore Drive and the Time Crystals, jumping to a different time period has always been a possibility. "What's Past Is Prologue" made time travel a possibility with its nine-month baby step. It was a possibility from Day One.
There's no Spore Drive that's used in TOS or the later series. It has to be written off as a failure. But they can't get rid of the ship before the end. I've said all along something has to happen to the Spore Drive. Something has to be wrong with it. Stamets having Tartigrade DNA and is one part of it. The Federation being against genetic engineering is another. No more Starfleet Officers with Tartigrade DNA. Discovery entering The Mycellial Network disrupts life inside there and creates an imbalance. The ship disappearing is the final nail in the coffin. The Spore Drive is operated by means that aren't considered kosher, disrupts an ecosystem, and is something they weren't able to effectively figure out how to duplicate without any of the drawbacks. Which is why it's not used in TOS, TNG, DS9, or VOY.
If Discovery can figure out how to use the Spore Drive effectively and work out all the kinks, then it
has to take place AT MINIMUM
after those series. If it takes place during the Picard Series, then
Discovery and the Picard Series have to worry about stepping on each other's toes. By having them take place 800 years apart, it becomes a non-issue.
Because
Discovery has to take place after the other series for Discovery to have mastered the Spore Drive and use it effectively, that must include traveling to different points in time as well as space. So there has to be a reason Discovery can't go back. Having data inside of it that can't be erased but is also something that Control can hijack, interface with, and compromise is a reason. Discovery can't go wherever or whenever Control is. And if Zora's existence turns out to depend on whatever data Discovery has that Control wants to seize, then she can't just be wiped out. So that could be
another reason. But Zora might be willing to sacrifice her life for the Greater Good, which takes us back to: Control. And maybe Zora's existence is independent of whatever data Discovery has that Control wants. Or Zora turns out to be selfish. Who knows? But whether or not Zora factors into it, Control is already one factor limiting their return.
I feel the same way as when people say they want a Trek series in this era or that era, what stories can you tell in the 29th that you can't tell in the 23rd? If they want to do the great unknown, there's, well, space. If they want to do isolated starship, Voyager has shown that doesn't need a time jump.
Stories about or involving Zora. Stories about or involving Terralysium. Stories about (but not necessarily) the fall of the Federation or, to flip it the other way, what it evolved into. The crew having to adapt to a new time. Stories about the V'draysh and Alcor IV.
Oh, and stories where Canonistas don't throw up their arms and say "How come we didn't hear about this in TOS?! This is anachronistic! What about TNG? What about DS9? What about VOY? What about whatever else I can reach for?" Now I know how fans of ENT felt. I've had just about enough of that crowd. Without fail, they're always there to chime in about anything new DSC does or has, and how it lines up with The Holy Canon. Like clockwork. It gets annoying.
Really annoying. Especially when it's all the time. The less they have to work with, the further they have to reach, the less ground they have to stand on.