In all the Portugal vs. Native American civ for the last one, I think Portugal is going to win. Why? Because it's in the name of the controversy: Portugal vs. Native American.
Some people are advocating for a Native American, but a lot of people don't really know which one... Haudenosaunee, Comanche, Sioux... We hear a lot of name, but there is not a heavy, strong consensus toward one Native American civ to be implemented. It's not a focused demand, a focus fight, it's broad and kinda loose. Lots of civs are wanted, but in the same way lots of SEA civs are asked without truly pointing and pinning one and one only name.
On the other hand, you have Portugal. Everyone is talking about Portugal, and Portugal itself. Portugal, as a civ, is alone in the fight. Every contender for Portugal knows which civ they wants to defend: Portugal. Portugal-defenders are talking about leaders, abilities and stuff like that. We know basically what we want: exploration, maritime trade, colonization... But for a Native American civ? All propositions we hear here (except for some people) are vague, unprecise.
If Firaxis people choose Portugal as the last civ, they already know which direction they're going to take, and the name recognition is far better and way more people would want to buy it.
If Firaxis people choose a Native American civ, they will have to face yet another hard choice: which Native American civ? And after that, thinking about the leaders, the abilities.
Just for this, just because the all controversy and discussions are around Portugal vs Native American and not Portugal vs Comanche or Portugal vs Sioux or Portugal vs Haudenosaunee make me think that Portugal already won.
Which, for me, is good, because I love Portugal, even if I would have wanted more extra representation outside of Europe; but for this, it would have needed work way prior (seeing Scotland as totally unecessary representation, having two Catherine de Medici, Alexander on top of Greece, Byzantium as a redundant hellenic civ, too many post-colonial english civ (one is good (America), two maybe, but three... Canada or Australia are too many, and even both... It's worse if you consider Gandhi as the fourth one)... one post-colonial civ for each imperialist sphere of influence -UK, France, Portugal, Spain & Netherlands- should be enough and even maybe too many). But, for now, knowing what we have left (and considering that we might not have a FFP), I think Portugal has way better chances to be revealed, especially as the very last civ.
And for all the people wondering: "What could they possibly do with Portugal? Aren't we stuffed enough with trade maritime powers with Phoenicia, the Dutch and Spain?" and I'd say: look what they gave us with Babylon. Babylon was always the turtle science civ, and lots of people would have guessed they would be a third Korea/Maya... And they gave us one of the most intelligent and fun design possible. So I guess that if Portugal is present, they would find a way to make it unique and fun too.
Edit: as for a possible Feitoria similar to the one they gave us in Civ V (which was one of my favourite UI), they showed us with the Vampire Castles that it was perfectly feasible to have an improvment built outside your territory and still giving the yields to the capital. So I suppose, if we have Portugal, to have a similar design for their UI: a feitoria that can be built only outisde their territory (by a Nau or a builder, in neutral territory or in a city-State territory or a territory of another civ in which you have an open borders treaty), doubling the yields in the six tiles around it and shipping them to the capital... Which would be beneficial to have feitoria in your empire even if you're not Portugal because you'll be beneficing from the doubled yields around the building, making other civs less inclined to destroy it. A beneficial system could appear in which the host empire improve the six cases around the Feitoria (by building mines, farms or even districts) and the Feitoria doubling them (and them copy-pasting them to Lisbon).
I agree. I hardly see them cutting through Portugal, this has been in the game since Civ3, which makes it as much a staple as, I mean, Byzantines and Korea. Portugal should definitely be in the game, there is not much to discuss here, it is too important, more important than many European and European derivative civs already in the game.
As far as more Native Americans are concerned, I hope it has some more post-NFP content to fill the main gaps: One or two North American civs, Maghreb, Italian representation, Assyria and... an Egyptian alt-leader.