I assume the game is mostly made up of content they had made for URU Live. It will have an updated URU engine, but it will be fully playable with a one button mouse (like Myst I-IV). It will also have a free roam mode. The physics based puzzles in URU, while a neat idea, were poorly executed, and avatar control was difficult for some players.
Even a point and click hotspot game will benefit from a fully 3d engine though. Most of the puzzles in MYST IV had to be covered up so you couldn't see them from other areas. Transitions were often confusing or disorienting.