realMyst was made by Cyan. Riven is waaaay too huge a game for Cyan to remake it, so they let 59Volts do it for them.
...and there's more than 3 games. Six technically.http://www.mystonline.com https://www.google.com/search?q=myst+iv+revelationhttps://www.google.com/webhp?hl=en#hl=e ... nd+of+ages
...and if you haven't heard, Cyan is making Obduction, a spiritual successor to Myst right now, but that's not to say there won't be any more Myst games. Currently more games are planned to go with the Myst TV show: https://www.google.com/search?q=obductionhttps://www.google.com/webhp?hl=en#hl=en&q=myst+tv+show
..also there's Robyn Miller's unknown game project being made with some old familiar faces (Richard Vander Wende maybe?). They have a concept tumblr here: http://nestingdollsimages.tumblr.com/page/2
So yeah, that's what's going on in the Myst fandom.