Nice idea, however the style of projector (excluding the room sensor) used in that video usually costs 2 - 4 times the amount current gen console sell for. So unless Microsoft have found a really cheap way to manufacture them (don't forget the cost of the actual console), it just looks like an expensive gimmick peripheral.
specially at the release date, but it will get cheaper after 6 month or a year
also developers will make more games that use those features
i remembered this commercial (i saw a year ago) it's pretty impressive, i really don't know why there is only a few people who use this technology till now http://www.youtube.com/v/iu1-KXsJ_Yw?version=3&hl=en_US&start=