Desmight: Looking at how successful have been streaming services for other media (music, movies, tv series), I think it's just a matter of time anyway. As soon as they get rid of input lag and as soon as internet connection become fast and reliable for most people, game streaming will be the standard and we'll all look like dinosaurs that refuse to evolve waiting to be killed by a meteorite :p
I have no doubt steaming will become more popular, but like we have seen in other media... I doubt it will take over, at-least not anytime soon, rather it will coexist peacefully with the traditional way of doing things. Even in music and movies, steaming hasn't outright replaced owning media, not even physical media like Blu-rays or CD's which still brings in a lot of money. And we can contribute that to older people still like owning stuff, and because people tend to treat Netflix, etc. as a glorified rental service and do buy media that they plan to watch more than once or twice.
There is also the issue that, at-least here in the states, internet seems to be getting progressively worse.. not better. Your big cable companies own most of the ISP's here and they are not going to let streaming replace their traditional business which is why we have bandwidth caps, etc. 4K is also starting to take off now, and with movies pushing 100GB in size, and internet getting worse, I have feeling we may see a significant shift back to physical media soon.
Let's take for example Comcast, in a lot of places they have a 1 TB limit. Download a few 4K movies and a couple of games and there is your internet gone for the month.
So steaming? I'm not to worried about it right yet...