Well, we have to see what we loose and what we gain. It is like that everywhere. You would think photoshop would never replace pen and paper and darkroom. Or doom would never replace paintball.
Ofcourse, if they can make **fast enough** and fun games that you don't need to download they'll be very popular. Plus they can stick an advertisement on the online version and make it free. Which is why many people would rather play the free one rather than paying to buy it.