I can't find a transcript, but based on what Christian said to Jack, I think what happens in the group at the end is really left to what you believe happens. The series while having plenty of faith and lots of ideas about religion, is never grounded in a single belief. Someone with a christian background may believe they go to Heaven while someone with a Buddhist background might believe they find Nirvana. In the Buddhist faith, Nirvana is considered a reawakening or enlightenment so there's certainly a case to be made with the characters realizing what happened in their life. Along with Locke being at peace. And can also explain why Ben and other characters weren't ready to go.
Reading up on Nirvana makes me lean towards that ending but it is in no way a definitive possibility and that is what makes it great.
You could probably also make a case for some form of reincarnation if you really wanted.