I don't understand why some people keep saying that Tablet is the "new" way, and desktop is the "old"/"classic" way. It seems they misunderstand something very basic. Rather,they are just DIFFERENT ways of doing things and are co-exist together.
Let me explain.
Tablet and mobile/Touch devices are growing but it will never "replace" desktop computing. As long as human being sit on a chair and work in front of a table. Years ago, people won't be able to use computer efficiently while "moving around". With the introduction of advance mobile devices, it is now become possible. However, it's the funniest joke I've ever heard in my life to claim that mobile devices will replace desktop computing. If you say tablet is going to replace desktop then you are claiming that in the future, people won't sit and work in front of a table/desk in the workplace, which is the most comfortable position to work for thousands years! It is uncomfortable to use a touch devices in this static position. E.g: raising your arm to reach the touch screen monitor? Bending your neck to work on a tablet? Definitely not for a long duration..This is just backward thinking if you are trying to use those devices in a non-moving position. Tablets and mobile devices are only great while you are in motion or short-term data consumption.
Windows RT/8 will be successful due to the fact that Tablet market is growing, but they dare not to remove desktop mode in the future. In a desktop environment, desktop mode is still a lot more efficient than metro mode.