Cyan has decided to announce a Riven remake as opposed to another Myst remake, which is pretty cool because this will be the very first time that Riven will be remade. It's kind of weird that it took 25 years for it to happen, especially considering Myst seemingly keeps getting updated every console generation, but hey, we're finally receiving it now so let's not look a gift horse in the mouth, eh?
Like the Myst remake, you shouldn't expect a remaster of the original game. According to Cyan's FAQ, it's a modern remake, which might send a shiver of fear down your spine, but the last Myst remake was pretty good, so we shouldn't have anything to fear on that front at least. What you should be afraid of is the potentially long wait between announcement and release, because at the moment all we really have is a very small trailer, an FAQ, and an open letter describing the history of the Riven remake.
Basically, the Riven remake began 13 years ago under The Starry Expanse Project. Cyan is a small indie company and didn't have the funds to remake Riven, so the volunteer team tried to do so in a "fully-realized realtime-3D environment", which sounds horrifically time-consuming and difficult. Still, these are fans of the Myst series, so solving difficult puzzle after difficult puzzle is another day that ends in "y" for them.
A couple years ago, Cyan found itself in a place where they could remake Riven, so they spoke to the Starry Expanse team and came to an agreement by which the team would "reference core pieces of [Starry Expanse's] efforts to jump-start our development". This meant that the fan remake was quietly canceled (with one member of the team being hired by Cyan) and efforts subsequently began at Cyan, with the fans at Starry Expanse having assisted with those efforts. Neat. In case you're wondering, Starry Expanse still exists; it's just not working on the Riven remake anymore.
For more information on the Riven remake, which we'll hopefully get in the near future, stay tuned to TechRaptor.