Although this article is a bit old now, it has the most details on the Myst TV series and a lot more input from Rand Miller as well as Blake Lewin of Cyan Inc.. There are apparently a lot of Myst fans at Legendary Pictures, which sounds very good;
http://www.spokesman.com/stories/2014/oct/14/cyan-agrees-to-myst-tv-deal/
November 6, 2014
Myst Movie Fans 
November 10th, 2014 at 9:14 pm
Knock on wood (like the tree elevator) that everything works out ok
November 29th, 2014 at 6:04 pm
If Yeesha appears there as an adult, I really think Juliette Gosselin should reprise her role as her there.