How do Pip's great expectations come true?

Pip's "expectations" come true only in the most ironic of ways (and even then, only briefly). Pip becomes obsessed with becoming a gentleman after meeting the beautiful but cruel Estella while playing at the house of her wealthy guardian, Miss Havisham. When Mr. Jaggers, Miss Havisham's lawyer, visits Pip several years later and informs him that he is due to inherit a fortune, Pip assumes that Miss Havisham is his benefactor. This in turn leads him to a second conclusion: that Miss Havisham intends him to marry Estella. With this in mind, Pip leaves his blacksmithing apprenticeship and goes to London, where he receives a gentleman's education and lives on an allowance as he waits to come into full possession of his property.
Shortly after he turns twenty-three, however, Pip returns home to find Magwitch—the convict he helped escape years earlier—in his apartment. Magwitch explains that he has been Pip's mysterious benefactor for all these years; Miss Havisham had simply led Pip on as part of her greater scheme to avenge herself on men. Pip is horrified to learn that his future is not at all what he had expected it to be:

Miss Havisham’s intentions towards me, all a mere dream; Estella not designed for me; I only suffered in Satis House as a convenience, a sting for the greedy relations, a model with a mechanical heart to practice on when no other practice was at hand; those were the first smarts I had (chapter 39).

He further feels that he cannot accept Magwitch's fortune, knowing that it came from a convict, but this in and of itself poses a problem because he is by this point deeply in debt. Ultimately, Pip does warm to Magwitch and helps him in his (unsuccessful) escape attempt. In the end, however, he has little to show for his career as a gentleman beyond self-knowledge: Estella marries Bentley Drummle, and Pip is saved from debtor's prison only thanks to Joe's kindness. Dickens even subverts another common literary trope when Biddy, Pip's faithful childhood friend, declines his marriage proposal in favor of Joe. With nothing left for him in England, Pip joins Herbert in Egypt and begins working as a clerk, ultimately achieving modest success in this position. As for Estella, the novel is ambiguous; Dickens wrote two endings, one of which holds out the hope that Pip and Estella may ultimately end up together, in partial fulfillment of Pip's early "expectations." The original ending, however, makes it clear that the two go their separate ways.