Spoilers below for the first Myst game.. be aware, thanks.
I once saw Rand do an interview where he basically said Cyan is not really interested in doing a 'Myst 6'. Tho he did say that might change if there were actually investors asking him to make a Myst 6 on their dime.
Still, tho.... if I were a Cyan employee, I would at least consider the idea of a Myst: Revival kind of game that combined all the Ages from the games Myst & Riven, as well as all the Ages that were available in Exile-- Basically any Age spawned before the events of the first Myst and was therefore written by either Atrus, Catherine, Anna, or Gehn and would be accessible from the Myst library.
It would contain the same events of Myst-- it is a revival after all... only, you'd have the option of playing as The Stranger, OR as Achenar, or Sirrus (or, who knows, even play as Atrus!!!). The extra Ages from Myst 3 would each contain a green page, to help release Atrus, and a brown page to release someone from Riven.. hopefully Catherine, but who knows?!? What if it is Gehn? Maybe the trapped character in Riven can only send letters to the player & you can't see their face or hear their voice...
Playing as the stranger-- the events after the ORIGINAL Myst game would just continue from the fireplace with new content where you have to gather a green or brown page from each Age, and these would be the Ages Atrus wrote for Achenar & Sirrus to learn the skill of Writing... those from, I think, Myst Exile. But playing as one of the brothers, you have the option of releasing Atrus, whoever that is in Riven... or go back thru the Myst Ages and release the other brother. You have to weigh which of those 3 will be in your interest to release. Multiple new 'bad' and 'good' endings, therefore, allow for LOTS of replaying...
Oh.. and the whole thing would use the same style of graphics as Uru, 3d rendering and a customizable avatar with early 1800's clothing... . which, the Stranger might be Mexican or Native American as well as European descent... which would be cool to play around with.
And, of course, the WHOLE thing would be a sandbox environment where you can dig thru and find all sorts of canonical easter-eggs that any seasoned veteran of the Myst games would giggle over.
That's just an idea that popped into my head; thought I'd share.
_________________ 
|