Details of the next few new episodes of Series 12 confirmed in the latest issue of DWM today. After this weekend's Orphan 55 which involves that big new monster which looked a bit like the Creature from the Black Lagoon attacking a holiday resort (Tranquility Spa), we have the clumsily titled Nikola Tesla's Night of Terror. This is the one in which Tesla and Thomas Edison encounter Anjli Mohindra's arachnids Queen Skithra, set in the New York / Niagra Falls in 1903. Episode 5 is the Judoon one - Fugitive of the Judoon. Only a single partner, as Episode 6 is Praxeus, whose synopsis mentions the Doctor having to tackle multiple incidents across the globe. Apparently this is the one with the swarms of black bird-like creatures (which might just be black birds).
This latter episode got me thinking about the theme which Chibnall said would run through the season (as opposed to a story arc). From what we've seen so far I suspect this might be something to do with tempering with nature. Spyfall was about rewriting human DNA. Orphan 55 might revolve around the creature fighting back because the holiday resort has been built in its habitat. Praxeus possibly about wildlife turning against humans? We know the Cybermen are coming soon, and they're a perfect example of what happens when science interferes with nature. If there is a Mary Shelley story (other than the Cyberman one) then that obviously also ties in with humans tampering with nature. Back in the summer there was mention of a story revolving around environmental issues, like plastics in the oceans.
So that's my prediction for Chibnall's series theme - tampering with the forces of creation, as Daleks were also once wont to do.