At D23 during the Parks and Resort panel, there were no dates mentioned or even if it was early or late 2019. What was stated is that SWGE at
Disneyland would open first. Given that SWGE at Disneyland is about 6 months ahead of the one at DHS, you could infer that the opening at DHS would be around September (provided that the Disnelyand version opens in early 2019).
I do not know if any of the Disney Parks Blog press releases had more date information.
Some people are thinking that it is possible that a potential soft opening could happen in December 2018 for Disneyland. This is all a guess based on how far along they are with the various show buildings. As we move into 2018 and see how far along Disneyland's version is, we will probably get a better sense of when a potential soft opening or actual opening will occur.