The devs said the new world would be split between two huge empires. Presumably if the Aztecs managed to hold onto any land in Europe during CK2, they still have it. Also, this:
"Rumours have reached Europe of a titanic struggle taking place across the Great Sea in the homeland of the Aztecs. The Aztecs themselves rarely discuss it with outsiders, but it appears they have been locked in a deadly war for some time with the Tawantinsuyu, a great empire from the mountains and jungles far to the south of Tenochtitlan. They are ruled by the Sapa Inca, who is allegedly the direct descendant of some kind of sun god.
If the stories are to be believed, the warriors of the Inca are armed with mysterious thunder-sticks capable of felling a man from great distance. The Aztec have only recently been able to halt their advance, in large part thanks to their mounted warriors riding horses imported from Europe."
So we should expect the new world to have gunpowder technology.