My take(s)...
Lori is dead....done deal. Greg Nicotero said she was dead, and the zombie had "drug her around the corner" & eaten her. He specifically mentioned Lori's hair in the zombies hands & in his mouth, which when I re-watched it twice, you can see if you're looking for it.
Carol...not as certain. I was thinking it's her on the phone from inside the prison, where you don't "need" electricity to work the phones, just phone lines. But, Nicotero said about the graves that one was Carol's grave, and Hardwick said "Carol's grave ?" Nicotero said, well, there's 3 graves, and one's empty, because there was no body of Lori's....I thought he might have lt a thng or two slip on the aftershow, but who knows ?
Nicotero did say we'd know who was calling Rick on the next episode....