Okay, I'm calling it. It's a grand strategy game in space (not a space 4x). My take on the hints:
1. This will be our first new major IP released since the original Crusader Kings over 10 years ago.
This excludes sequels to CK, EU or Victoria (HoI4 is of course also excluded since it's on its way). Also excludes sequels to minor games like MotE or Sengoku. A GSG in space would definitively be something new and something major.
2.Seven and Three are important numbers.
I have no concrete interpretation of this one. Many have related this to dates and years, but really from the meaning it could mean anything. My guess is that it's gameplay related. It could be seven great powers, three tech eras, something like that.
3. There will be no stabbing of pigs.
This hint points away from a spiritual successor to EU:Rome. Apart from that, it really says nothing. Sure, it could be somekind of troll attempt and there's no way to know. I take it and face value and see this hint as making a classical antiquity game less likely.
4. Terrain truly matters in this game.
Again, this could mean pretty much any game set anywhere. Many point out historical battles in classical antiquity, but there have been matters where terrain matters in wars in all eras. How would it fit a game set in space then? Well, if you see celestial bodies such as planets as the terrain, then itt's a dominant feature of colonisation, production, trade and possibly ground warfare.
5. Game Director is Henrik Fåhraeus, 15 year industry veteran, lead designer behind the Crusader Kings and Hearts of Iron series.
Again, this doesn't really say anything about the game. If there's to be an interpretation, I see this as hinting at that the dominant features of CK and HoI might be part of Augustus. Those are emphasis on characaters, and emphasis on warfare. I can easily see these fit a space setting. For instance, it could be something similar to the Dune universe, or to Emperor of the Fading Sun, both feudalistic systems set on a interestellar stage. Characters have been important in other space strategy games as well, such as the classic MoO2, with it's planetary administrators and ship captains. Another variant would be a Foundation-like setting, with a Roman analogy in space. Then it could draw on the excellent character mechanics from EU:Rome, with loyalty and civil war as big factors.
Couldn't this decisively point to classical antiquity, then? Sure, it might fit there as well. The hint in itself doesn't say much about the actual game, really.
6. Elections and Technological Development are important parts of the game.
This excludes some earlier candidates, such as a game focusing heavily on China or Japan (because of the elections), WW1 (because of the short timespan), Migrations Era (because elections were of limited importance and technological development as in developing new technology seems unlikely to be a big part of such a game). There were of course technological development in classical antiquity, so that candidate still stands. However, I wouldn't have guessed that tech development would be an important part of a game set in that era. Elections fit some parts of that world, such as Greece, Rome and some tribes, but fit others less well.
Does it fit in space? Well, technological development seems an obvious fit. Elections in space games haven't been done much AFAIK apart from diplomatic victory elections, but I can't see why they couldn't be done. Spacefaring civilizations might be feudal, imperial (with or without elections), democratic, authoritarian or anything between. Maybe in the game world, elections are common.
7. This is a project we've always dreamt about doing, something all of PI have been involved in, not just the PDS developers.
There have been comments from various employees in, for instance, the ask PI anything thread, where they've stated that they'd love to do a space game.
One example is @Shams answering my question like this
Shams said:
We'd love to make a space game. All we need is to fill those empty positions; http://www.paradoxplaza.com/jobs
/shams
People at PI love space games. Here's Kallocain mentioning EVERYONE playing EVE:
Kallocain said: ↑
Not right now, but when I started I had to start playing EVE to have something to talk about during lunch. EVERYONE played.
@podcat gives his two cents, again after a question from me:
podcat said: ↑
I think a grand strategy space game would be very cool, but I doubt we would want to work with existing licenses/franchises like the above. It introduces a lot of special issues and you might not get full freedom in doing what you like.
That said I personally would not turn down working on a Dune universe game or a WH40k grand strategy but I have a feeling "all the license stuff" would be pretty taxing, and I don't think its something the studio is interested in right now.
Here's another one from @podcat
Q: Will PDS ever release a 4x space-game ?
A:
podcat said: ↑
That would be pretty cool. its often something that comes up in discussions at the pub so hopefully some day
So, in conclusion, it's clear that people around PI, from PDS devs to publishing staff would love to do a game set in space.
Bonus hints: The Trademark lead
PI have filed a couple of trademarks that don't correrspond to current games. Two of them, Stellaris (filed 30th of june 2015), and Coriolis, fits a space game. Coriolis is a book set in space published by PI. It's set in the same world as a table-top RPG developed by people linked to PI. They describe the world like this: "The RPG is set in a world of Byzantine intrigue, gigantic spaceships and secret remains of earlier civilizations".
My bet is that the game will be called Stellaris, set in the Coriolis universe. Many have doubted PDS's capability to creatively come up with a setting for a non-historically game. Here, through an IP they're already involved with, they have their setting.
There's also never been any trademarks that might fit a classical antiquity Augustus game.
A counter-point to the trademark lead is that it was filed too close to announce. However, that was true for Cities: Skylines as well. That trademark was filed just prior to announce at Gamescom last year.