Veras
Prince
Personally I bet we get a Japanese sponsor, one other European sponsor, and two wildcards - perhaps something from Central America as you say.
As a Tropico player I've entertained the silly idea of a third world backwater island dictator somehow stealing a seeding ship.
I remember from some interview that while the 8 original sponsors were leaving Earth, the others from RT were struggling to reclaim their homes and, presumably, to survive. I don't remember if this aplied to all 4 or just Al Falah, but, considering the first is true, we may draw some conclusions:
-All new factions come from places that were highly vulnerable to climate change, wars or other humanitarian crisis. Taking Al Falah as an example, the Gulf States (from where I presume they came from) and the Tigris-Euphrates basin are highly vulnerable to the rising seas, and they were also very close to the nuclear wars in Central Asia. Other vulnerable places are precisely the Caribbean, the North of Europe and Japan. (There is also Antarctica, but I just can't imagine something coming from there)
-It probably took many decades, if not a century, for some of these factions to catch up to the point of being capable of pursuing the Seeding. So rather than a third world backwater dictator stealing a ship, I imagine them fighting to survive until reaching the point where they figure it out by themselves how to escape Earth with their limited resources (or just waited until their insufficient resources became sufficient). Al Falah, for instance, may have needed a huge amount of time to build their generation ship, which had to be much larger than normal ships to house a living community for centuries. Better FTL technologies available and tricky quantum physics will do the work of putting them on a planet at the same time of the original sponsors.