The debut of the Wii was an interesting time the gaming industry. Nintendo was taking a step in a direction that hadn't even been thought of before and nobody knew how it was going to turn out. Gaming journalism argued about it again and again but it was such a different idea most consumers were unsure of what to expect from this new system. The Wii sold at first primarily to gamers but quickly expanded into markets that game companies had not touched before. This led to group of consumers who would not classify themselves as gamers but used gaming consoles.
This distinction is important because the while the Wii was able to add a large market for the gaming industry Nintendo has had trouble in converting this market to additional software sales. Many people who were not gamers purchased the Wii as more of a toy and less of a gaming console. The difference being that they buy the console and an occasional game but it does not make a big deal of their is little new software for the system and they don't really care about the next generation of systems.
As Microsoft tried to access this new market motion control accessed a new group of people in a way Nintendo had not. I know a lot of people who own a 360 but weren't interested in the Kinect, however another member of the household purchased it and used it profusely. The Kinect has sold incredibly well and I would say it is largely due to situations similar to this. Motion controlling is often a turn off to gamers but it is such large market it absolutely going to be a continued part of the game industry.
This brings us to the question of the future of gaming and motion control. There have been rumors of the next PS and Xbox including motion control. While they are tied together in many ways they don't have to be forced into a single entity. I personally do not want to have all games use motion control, when I buy Wii games I will normally play with the classic controller if possible.
The best answer for this is to keep motion control as and addition to a system and not a primary component. With more and more household having consoles it is easier to market just the peripheral to a consumer interested in that aspect of gaming then having to sell a full system to them. However a consumer that doesn't want motion control doesn't need to buy it for his/her games. Most importantly, by keeping this separation developers will feel less pressure to make use of motion control in a game that may not benefit from it.