Guillermo del Toro recently said that he had to drop out of Justice League Dark because of a schedule conflict, that it was going up against Pacific Rim 2. If a new report in Canada's Global News is right then Warner Bros wanted JLD to start right away, as they're saying Pacific Rim 2 is shooting in November at Toronto's Pinewood Studios.
The report also says that the working title is Maelstrom, although whether that's the production code name or the actual subtitle; the first film went under the name Still Seas while in production. I do think Pacific Rim: Maelstrom sounds totally kick-ass, though, and I welcome that as its title!
The new film will, according to Guillermo, focus much more on the kaiju this time - a welcome change, if you ask me. While I loved the Jaegers and their pilots, it felt weird watching a Guillermo del Toro movie that wasn't siding completely with the monsters.