It will be just one dominant terrain type. Not that realistic but much better than now. One interesting question is what is the dominant terrain type on Earth? At the moment I am leaning toward Temperate Forest, although I could perhaps add some form of mixed terrain type with a single set of values.
A very strong argument can be made Temperate Forest is correct. With the increasing temperature that can change (the most plausible end result from current data seems to be much greater desertification until rain patterns stabilize, at which point the savannahs and tropical forests are liable to grow. Time until that happens; unknown). I'd rather not have Earth create an exception though, so use the single biome system.
I understand why you use it; it's much simpler than the alternative.
Also, whenever I find a planet with a Mountain base terrain I'm going to raise its temperature to 35 degrees. It means the only possible result is jungle mountains.
There is no biosphere concept at the moment, although I will probably add indigenous lifeforms that could pose a threat to any colony. The new ground combat system will allow a wide variety of potential non-sentient foes. They would have to be cleared, or at least defended against, to ensure the safety of any colony. Any local wildlife would be adapted to the environment and have appropriate capabilities.
Please don't go for the standard 'hyper focused super predators obsessed with eating man.' It's stupid. Rather, go for something that cannot meaningfully impact settlement. I mean, seriously, bears and lions and wolves and large cats are really dangerous animals, make no mistake, but wolves and bears went
extinct in much of Europe for a reason, and we've got much better weapons these days.
No group of wild animals could meaningfully impact a planetary population of humans, especially when said population is armed with and/or protected by armed people that carry military weapons and information gathering tools. Microbial life is far more dangerous because it's harder to detect and easier to spread, while a rush by even a thousand heads strong herd of cattle would not do more than destroy one or two villages before heavy weapons turn them into mince.
You would need alot more then 12 billion population on Earth for Urban to become the dominant "terrain" for example.
Not really.
Dominant Terrain doesn't really describe the dominant terrain of the
planet, it describes the dominant terrain that is being fought over. Since the invention of rail travel we've been seeing a lot of consolidation of populations into cities and away from rural areas for a variety of reasons, but the two biggest factors are to do with farming automation greatly driving down staffing requirements for food production, and rail ways making it possible to bring all that food large distances. Without either of those factors population centers would've been much smaller, much more numerous and more scattered.
This will be something that affects our settlement pattern on other planets too.
With farms and food processing systems that are completely or nearly completely automated and the ability to ship their produce across a continent in days and thus before it spoils there is no incentive to create an expansive network of cities across a planet based on the availability of food. Worse, with the fact that trans newtonian technology apparently comes with nearly limitless energy for free you aren't even limited anymore to things like seasons, the sun and weather patterns; all production can be done indoors in vast glass houses with machinery rolling over tracks along beds of produce.
Instead, you are liable to see cities settled on and around places rich in mineral wealth and all food shipped in or produced in hydroponics systems, where the first mines on the planet are established along with the refinement plants for those minerals. Because a ship and harbour are much easier to build than an expansive railway network and you are going to need water anyway these cities are likely to be build on rivers and close to the coasts of large bodies of water where possible.
New mines will radiate out from these new cities but not be followed by new refinement plants unless production capacity becomes enough in demand to establish new plants and doing so is cheaper in the long run when done close to the mines. This is because transportation is dirt cheap with boats, and once the infrastructure cost has been sunk dirt cheap and fast with trains.
All of which boils down to one thing; once planetary population becomes numerous enough nearly all things worth fighting for are in urban environments. It doesn't matter if this means bridges, factories, government offices or something else; you cannot meaningfully impact an enemy's combat ability without having to go through urban environments to get there even if those things aren't in an urban environment.
And that means urban environments are the dominant terrain of those planets. That's where you fight.
Of course, urban terrain as dominant terrain is going to suck
horribly for the civilians. Collateral damage is going to sky rocket in comparison to... pretty much every other type of dominant terrain.