I agree, personally I would be perfectly satisfied with a Civ7 that leaned heavily on Civ6 and Civ5 but actively tried to improve on the features that didn’t work optimally - modular game elements, combat system, district and building yields, policy cards and governments, and victory system (particularly religious victory), to highlight a few - and taking inspiration from sources like other games (Humankind, Old World) and mods (City Lights, Terra Mirabillis, …) and also trying to make the AI handle the game elements.
I see a lot of negativity towards Firaxis and Civ6 by certain posters in this thread, but imo. that’s neither fully warranted or a constructive approach - yes there were flaws in Civ6 that probably could and should have been avoided, but bringing many new elements to the table always means you need to tune things to get it right, which is why I hope they don’t throw everything up in the air again.
The old saw is a new game should have 1/3 Old, 1/3 New, and 1/3 Revised, I believe.
Let's see if we can start a sort of constructive discussion (although I suspect at the basic level Civ VII is far past this by now) on how those could break down for the Next Game (Probably Civ 7, but if they name it Civ 6.5 I would not regard that as a Positive Sign).
Old:
1. Animated and Voice-Acted interactions. Now in the past that has been Leader Personalities, and I strongly suspect they will stay with that, but I would love to see some Non-Leaders recognized as such, given the animation/voice treatment and included - the place for folks like Richelieu, Thomas Cromwell, Jeanne d'Arc - even Rasputin and Trotskii for complete Outliers.
2. Most or All Civs available from Start of Game to End of Game. Humankind has taken an entirely different path with their progressive Era-Civs, but it has not gotten universally positive reactions from players, and I really doubt that Civ will go anywhere near it.
3. Commentary. They've used Tech and other comments for several games now, it's a safe bet they will continue that. Since as many people like them as loathe them, I don't think there's a great need for change, but hopefully they will pay more attention to proper pronunciations and less to having a 'name' do the commenting.
New:
1. A Tactical Battle System. ALL Civ games have always done all combat on the Strategic Game map, either by 1UPT or Stacks. I think they will finally break away from that, BUT I am equally certain they will not 'copy' some other game's system: there are flaws in all of them and I think they can do better if they put in the effort, and I think a really good, smooth, tactically-complex but not time-consuming system would be one of the best single additions to the game.
2. A Real "Rise and Fall' system. They've skirted and poked at one for several games now, and never gotten it right or made it particularly important. Something that does not produce Rage Quits but does produce major changes in the Civ (which would address the idea of a 'new Civ' later in the game without modifying the basic One Civ Per Game playstyle) which the gamer has to address would be another Major Change and plus for the game system, IMHO.
3. Interaction with the In-Game Events. Again, they've skirted this in the past, with the Recently-added-by-Mod-to-Civ VI upgradable throne rooms and palaces and similar, but never really gone 'all in' with it. Having ancient Wonders become the basis for later Tourism Centers, a running Chronicle of gamer/AI achievements in the game, the ability to chage things on the map to reflect the Greatness of the specific Player-Character (why can't we set up a Monument to Ourselves? Almost every one of the Leader Characters they are depicting for us did it. This would also build on Civ's distinctive Personalized Characters in the game, which they are almost alone in the 4X genre in having the resources to do them complete with animation, voice acting - and on-map, in-game interactions, constructions, etc.
Revised:
1. The Trade System. I put this first mostly because I've posted at length on this before: the game now has two trade systems, one for Resources done entirely by diplomacy and ignoring all the rules of travel tech and distance and one for on-map Trade Routes that is severely restricted by technology, distance and Enemy Action. At the very least, the new game needs One Trade Route/Trade System with one set of rules, covering everything about Trade, including the diplomatic requirements and (another bit I would personally love to see) Illegal Trade, smuggling, etc.
2. Units. Including Promotions, Upgrades, Tech, Civic, and Social Policy requirements. Again, they've
'dipped a toe' in some of this with the GDR's Technical Upgrades and having a few Units with Civic requirements in Civ VI, but they need to go All In. Armies should reflect their society/state, and this would be a major change from previous Civs, but could be done by building on the 'bits' they've already tried.
3. Tech, Civic, Social Policy 'Trees'. Keeping Tech and Civics separate will stay, I think, but the interaction between the two and the Social System your Civ builds and maintains need some serious revision. More consequences for changing, and consequences in more areas of religion, diplomacy, even Technical/Scientific progress and Loyalty/Happiness within your Civ. I think the 'Tech Tree' is long overdue for a revision into something resembling BE's "Tech Bush" but much, much better done, or even SMAC's semi-blind Tech Progress, but the point is there are lots of ways to improve these systems and I would be extremely surprised not to see major revisions in them.