source: Summer House was/is casting so some people will definitely be leaving. And/or they’ll be new faces.
Final cast is not decided until very close to filming. The main players know but some are just told to clear their schedules, things change throughout the summer even.

Allegedly from bravoandcocktails.com
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Please no Danielle
I’d like to see everyone except for Danielle come back. I just don’t think she goes well with anyone, not even Lindsey. Replace her with Jordan from SHMV (if there’s no season 3 of MV, that is).
I honestly don’t want them to change this cast. Though Danielle annoys me, I don’t want to see her go bc then I will have no one to hate on.
Agreed
Really want West and Jesse back. Paige must stay and one of her friends (past or present). Kyle and Amanda should leave for the sake of their relationship. I’m fine with Bravo changing the rest.
I’m good with Carl being part-time. Want to see the dynamic between him and Lindsay but not like the entire season. I’m ok with Danielle part time too.
I’m good with all the cast coming back and okay with some being demoted or just in a few episodes and adding new people.
I want some fresh faces and some housemate hookups! When everyone is in a relationship it’s boring