I could see it going either way, frankly. Endgame is probably gonna clear $2 billion, easy, but Pokemon is the most profitable media franchise in the world. Bigger than Star Wars or any other superhero. And that's just in its relatively short 23 year lifespan. The games, cards, anime, and everything else are all massively popular even to this day.
So take that 23 years of historic popularity and profits, and now give it a genuinely promising and good Hollywood movie to finally cash in on it. And compared to many other Hollywood movies that compete against other similar movies, Detective Pikachu has no direct competition. It's not a superhero movie, it's not a straight action movie, not a thriller, not a comedy, not anything that fits into any easily defined genre. It's completely unique and something that hasn't really been done before.
It all depends on the final product; if reviews come in and it's actually a mess somehow, then that'll wound it. But from all appearances, it looks like the plot is fairly straightforward, being a detective story (which is a pretty genius move to keep things simple), while putting most of the energy and creativity into the world, which is going to be the most interesting depiction of the Pokemon world ever.
I'm gonna see it.