I'm assuming you haven't read the sneak peak at the end of Acofas, the book is obviously going to be set in Illyria and focused around cas and nesta. I do think elaine and either mor or amren will get povs on the girls side and lucien and azriel will get that love triangle. 

Hi, I’m sorry,English is not my native language, so I guess I couldn't express myself correctly before. I didn't finish reading acofas yet when I wrote this post. I just finished reading it and I realized that it will set in Illyria like you said. It seems to be an extraordinary story again. I can’t wait to read the rest of it. I'm very excited! I'll still miss Feyre's point of view, hopefully her and Rhysand’s  role will not be too small. Because I really worship them!

Me and u both I worship rhysand he is like a freaking god

I don't think that preview made it clear that it would be based around them. I think it'll still have them all in but maybe it has a centre-point of cassian and nesta's relationship. just because that preview was set in Illyria, it doesn't mean the whole book will be. I hope not anyway because I really want rhysand and feyre to have a major part in it