Theories

I think Max will stay in Paris and choreograph like his father and will also help Lena with the time travel.

I think Nico is from 1983 and he will jump thru the portal with the others, and Lena and the others will not even know that he was there with them.

I think that Nico is actually from 1983 and accidentally comes through the portal and Thea will go on a world tour with the company and others will be in 1st division.

Lena and her friends are going to ask for help to young Armando and reveal to him everything and i think that Armando will make sure that everything that has to happen in the future will happen.

I think that Nico will be one of Lena's best friends and that he will fall in love with Lena. This will make Max jelous and the two boys will hate each other.

They will go ask aged Claudine and reveals all the secrets to them, while Max does everything he can to bring back Henri, who has been deleted. They will also come back in 2019 and they will meet Nico a new student.