If we want to talk about box office results, we shouldn't look at what its total gross will be once its theatrical run is finished. What should be looked at instead is the opening weekend, and currently, it's projected to make somewhere in the
75-90 million range. IMDB (which I'm sure is where most of these "It'll hit a billion!" cries come from outside of one of the Marvel guys) has a
2019 box office prediction (for some reason, but whatever) where they feel
Detective Pikachu will be the third-highest grossing 2019 movie once all's said and done.
So due to brand recognition, the movie has a
very good chance of being financially successful, which is why Legendary announced a sequel as they're
that confident. Thus far, the budget hasn't been revealed, but on average projections place a blockbuster film to break even around the 500-mil mark (you have to take into account marketing, and Legendary alongside TPCI's
heavily marketing
Detective Pikachu). I personally like to look at domestic revenue for films, but for the past decade Hollywood has catered heavily toward the international crowd, especially China, so even if the film doesn't make much
domestically, it can rake in the dough overseas and still keep Legendary in the green.