I hope we see Sif, but I'm glad to see Portman go. I don't hate her, but she was the worst part of The Dark World
She's overrated--and yes, winning an Oscar does not make one free of that charge, since the voting often has much to to do with factors having nothing to do with merit. She brought nothing to the Thor movies, and only seemed to be cast based on some hope to lure the nerds who were still panting from her Star Wars prequels days.
having a Thor movie focus on Asgard/the nine realms instead of Earth or some human woman, would be a nice change of pace after the last two Thor movies (which I liked, but I've always wanted more Asgard stuff).
I agree--I used to love the all-Asgard stories from the Silver Age, and added much dimension to Thor that hanging around on earth (solo or with other heroes) did not.