I vote for the fact that the Romulans created the Borg thousands of years ago, perhaps inadvertently...maybe it's also related to V'Ger too I dunno.
I don't really like the idea of Romulans or/and Vulcans being Replicant style clones with wetware programming or biomechnical androids (and what's the obsession for organic androids? Being organic is, IMO, a regression and they'd just be tools/extensions for the AI nanomachine cloud residing in subspace).
Here's another nutso theory: 'Our' Lorca, in the Mirror Universe, discovers that they (the Mirror empire) wiped out a synth threat easily, early in their formation. But they only did this cause they had conquered the whole galaxy. Lorca correctly assumes in the Prime Uni, that this synth threat would grow unhindered. So he forms the Zhat Vash and sends them over.
I really, really don't want the Romulans and Borg to be connected at all. I hope the Big Secret is that all Synth Life ends up trying to become Borg - they see it as the end-result of logic and math and all that stuff, so developing Synths anywhere will, in time, result in a Borg or Borg-like entity that the Borg may subsume and activate. Data was going to become evil, or an unwilling pawn, or something (and that ties into Lore), and thus this is why Soji and co must not be allowed to live/propagate. It may be that the Borg were the result of the 'first' race to develop Synths, and I wouldn't mind if Soong got his tech from the Borg somehow, and the Romulans may be privy to some secret Galactic-Core based organization that is using all its power just to be something the Borg throw themselves at like a meat grinder (which may explain why the Borg are basically only just on the Scutum-Crux arm than the whole Delta Quadrant) It can also tie into the Galactic and Core Barrier things. Thus why the Zhat Vash exist and are so fanatical. Maybe the Romulans tried to develop AI and it tried to do a Borg on them/call them in which was repulsed somewhere off and at great cost long ago. Any AI will turn, in the terminology of Orion's Arm, Ahuman/ABiont and work from within to join the Borg and turn all Organics of any threat to mechanical drones under its control. The True Borg may be such a first AI or an collection of AI, and Synths fall into that category as being unwilling/suspectable Fifth Columnists. Thus, the only way to stop them is to never develop that technology at all, though why this doesn't extend to Holograms and Ships-turning-AI is beyond me. Also it's basically a rip-off of Mass Effect but the Reapers are still actively in the Galaxy and far weaker.
Eight synth models. Two are dead (Data and Dahj), one is alive (Soji), while the 'Final Five' will be revealed later. Sounds familiar??
I feel like it would go against Data's while story arc to establish that synths = bad no matter what. If Data can grow beyond his programming, any synth can, etc. etc. A very Trek theme.
This really goes against everything Star Trek stands for! It would make the end of Discovery's first season look like the pinnacle of ethics in comparison. I mean, as I said upthread, one of the central tenants of Star Trek is no race is inherently evil/bad. We may look different, but we are all "human" metaphorically speaking. Any time that it initially looks like a race of "bad guys" are rotten, we find out the underlying story is more complex, or they have understandable motivations, or it's just driven by out-and-out racist fear. For the Zhat Vash to actually be justified in their blanket fear/hatred of all synths, it would basically mean that Star Trek is saying prejudice is a good thing. Some beings might look just like us, but they can't be trusted because they can become devil-spawn who seek to kill us at any moment, so we should just genocide them to be on the safe side. Considering Trek often speaks in allegory, this would be essentially endorsing the anti-semetic "Zionist" conspiracy theories in Trek form.
I tend to think that Control is a disposable concept--enough of an antagonist that could tie together the disparate elements that made up the whole season.
Something like the circle shot was shown in the trailers before the series started, and it appears we'll see more next week. Some sort of Zhat Vash ritual? The first explody planet appears to be Earth. I can see Baja California. Further shots of a Romulan trying to bash his/her own head in - and a later one involving a self-inflicted disruptor to the head seem to be related to the knowledge that makes them "go insane" Lots of explody planets and such which are hard to identify. Aside from the one shot of a synth face (not shown in the images here) there's little which is shown to let us know the threat is synthetic in nature.
either the re-used those CGI scenes for cost savings or it is maybe related to Discovery/Control after all...
If I am not mistaken I do believe that someone at CBS, either actively working on the shows or in corporate, did say that they wanted to have connections between the shows.
There has always been the re-using of assets in the making of Trek so I'm not TOO plussed about that. But who knows! Really all we know is that the secret involves explicit planetary destruction that could cost "trillions of souls."