Microsoft desperately needs something that is suitable for tablets and the like. Thus Windows 8.
I know someone who has a desktop with touchscreen interface to Win 7 ... they quickly disabled the touchscreen and went back to keyboard . mouse with Win 7. They felt that touchscreen interface is not suited to desktop computers.
I, too, very recently bought a laptop with Win 7 Pro so I could get virtual XP on the same machine. I hope it lasts a long time.
I remain convinced that Microsoft has shot themselves in the foot in the desk/lap top market in order to compete in the (very important) tablet market.
How long before Win 9 appears? It could well be "what Win8 should have been". (cf Vista/Win7) In other words, Win 8 is not likely to have a very long life.