Steam already *is* that powerful.
The weird thing is the implication that the High Street retailers didn't see that coming.
Valve were rather large and well-known in the PC gaming sector even before they launched Steam, so it's not exactly surprising that they managed to leverage that to get so many third-party developers and publishers to jump on board.
Furthermore, while it does have DRM it's not massively in-your-face, like most of the other DRM schemes various publishers have tried. I'm not going to buy a game that treats me like a criminal in my own home.
However, I really don't like that I apparently can't gift my copy of a game to a friend once I've decided I don't want it anymore - maybe I didn't like it but a friend of mine might, or maybe I just finished the game and don't want to play it again.
That said, I'm not entirely confident that Steam will be around for longer than 10 more years or so.
However, I do think it'll probably be around for the useful life of my current PC.