The problem with Myst is every time a new sequel came out Ages, while looking better than the previous incarnations, got worse in gameplay and puzzles. Cyan should try and concentrate on creating original and innovative Ages while paying extra attention to the special magic that made Myst a fun game to play.
An idea is to let a well-respected fantasy author create an Age... then a Sci-Fi novelist... then a Horror novelist... and so one and so forth through out each genre. Could you imagine if someone like an Anne Rice or JK Rowling created an Age? I think this would keep me interested in Uru Live.