Yes there were rumors of Emma Watson to reprise the role but there has been no news about it.
I think she would be playing the role of young Natasha in black widow movie.

Yes,it is true natasha Romanoff in black widow movie

Yes it is 100% true. There are also some set photos of Scarlett holding a glowing object which may be the soul stone. We might see her being revived in the movie.
There are also some set photos with General Thunderbolt Ross, Red Hulk.
The movie is set to release on April 30th , 2020.

she is getting her own movie and technically if the soul stone was returned then doesnt the soul for a soul philosophy work in which cap can trade the stone for black widow