You can see in the gameplay vids that the effect is present. There's nothing quite as dramatic as the teaser but it still functions as a liquid. There's a tech demo floating around demonstrating this implementation as well. It's a big feature of the engine.
Show me the opposite. Where did you see traditional 2d fire effects in this game?
They still need a lot of work on that. Fire in last trailer was at 10fps or something.
Still they didn't even mentioned release Q so they have a lot of time to improve things.