I think you're confusing Riven with the original Myst. There have been full 3D versions of Myst since way back in 2000, but a real-time 3D remake of Riven has been a long-awaited pipe dream.
There was a long-running fan project called "Starry Expanse", aiming to recreate Riven in 3D. They got acquired(?) by Cyan a couple years back and their work got incorporated into the official Riven remake, which is supposed to come out sometime later this year.
It’s a few members at this point. I was on the SE team, very proud of my teammates (artists, musicians) who have gone on to join efforts with Cyan. The new Riven is going to be amazing.
Sorry, yeah, they didn't "acquire" the whole team in a business or employment sense, but my understanding is they got access to all the code and art assets they had created over the years.
There was a long-running fan project called "Starry Expanse", aiming to recreate Riven in 3D. They got acquired(?) by Cyan a couple years back and their work got incorporated into the official Riven remake, which is supposed to come out sometime later this year.