Dreams, hopes, plans … and Great Expectations. Fun fact about "expectations": having "expectations" in the nineteenth century specifically meant that you expected to inherit some money after the death of a family member—just like all of Miss Havisham's annoying relatives have. But they're not the only ones with plans. Pip wants to become a gentleman and marry Estella; Miss Havisham wants to use Estella to revenge herself on men; Herbert Pocket wants to become rich; and even Joe wants Pip to grow up and work at the forge with him. One by one, every single one of these expectations fails. But does that mean we shouldn't hope or plan? Maybe not. The only person who doesn't seem to have a dream is Estella—and we wouldn't wish her life on anyone.
Pip's great expectations are never fulfilled, but what he gets is even better.
The marshes represent a dream world to Pip. Even if he'd never met Miss Havisham, that world would have ended as he grew up.