Yeah, I think right now everyone is locked a bit in their thoughts on a one old-world continent, and one new-world continent.
But easy other options are:
- Old-world archipelago, new-world continent
- Old-world archipelago, new-world archipelago
- Old-world continent, new-world archipelago
In that way you still get a lot of options for early ocean-faring civs.
Not to mention: I don't think it has been said that there will be one old-world and one new-world.
There could easily be multiple new-world continents.
Or the old-world is split over multiple, which can only be reached in the 2nd age. So you get a colonized new-world, and an un-colonized new-world.
Or imagine a flat earth map, with one old-world in the west, one in the east, and the new-world in the middle.
Multiple new-worlds, potentially colonized also allows you strategic options:
- Do you load your fleet with settlers and scouts to peacefully colonize an empty continent? What if you find a full continent?
- Do you load it mixed, with military, to conquer some city states?
- Or fully with military, to conquer another old-world? But what if you don't find it fast?
And in which direction do you sail?
If you see that another civ is faster with dispatching their fleet, what do you do?
- Sail in another direction, hoping to be faster?
- Gamble on that they loaded their army in, and invade them?
There are soooo many interesting options.
As you mentioned, the poles might not work well, but I think that bonuses for circumnavigating the world (as in Civ3), and exploring the coast line of the new world will probably be a thing.
On the other hand, you need to see that Siberia was mostly empty, with very little humans, despite that there were not that many mountains.
Having a gameplay feature, which at least seems logical, to preven the colonization of the whole continent, would still be interesting.