I was actually laying awake last night thinking about it, that's what prompted me to get online and find out about the sequel.
But I agree the ending was inconclusive and led you to believe
Spoiler: (Highlight this box to see the hidden message.)
| That sarah died in the caves|
And I believe it should have stayed that way, From what i've read that's what Neil Marshall seemed to have wanted considering
that he is not back on board directing, just overseeing that someone doesn't ruin his good name.