It could happen but I wouldn't count on it since this is Disney's official announcement. I'm hoping for soft openings during our mid-September trip but honestly not thinking it will happen. So many things have not happened the way I anticipated when I first started planning this trip almost 1 year ago.
1. Mickey and Minnie's Runaway Railway - thought it could be open but delayed until 2020
2. Skyliner - was almost positive this would be open. Nope!
3. Star Wars: Galaxy's Edge - thought we'd avoid this 'late fall 2019' opening by arriving Sep 7. Nope again! Will be in the thick of it.
We've been blessed to visit Disney more than normal in the past 18 months and was really hoping after watching the Skyliner progress that this time it would finally be open!

Looks like we'll need to wait until our Sep 2020 trip to ride it now.