No, the title is not a typo. Although Lost Boys 3: The Thirst is still in production, Corey Haim is set to return to the franchise in the fourth installment. Here's what B-D is running...
After the events of Lost Boys 2, it was said that Corey Haim would not be returning to the franchise alongside long-time co-star Corey Feldman. Movieweb broke some huge news this evening as they're reporting that Haim will in fact star alongside Feldman once again, only it won't be in Lost Boys 3: The Thirst, which begins filming soon in Africa.
They report, "We just got back from chatting with Haim, who confirmed that he will not be participating in Lost Boys 3: The Thirst due to his very busy schedule. But he is in fact looking to come back for [LOST BOYS] Part 4, in which Sam Emerson will play a huge part in the storyline..." If the third film is as bad as the second, I don't think I'll even care at that point.