You know, despite the success of the PS1 and PS2, I don't think Sony has any idea what they're doing. They only succeeded with the PS1 because Nintendo shot themselves in the foot going with cartridges on the N64 and Sega fired a BFG 9000 at themselves. And with the PS2 they had no competition. I think Sony just got damn lucky and doesn't know how to compete with equals. Think Rocky VI. I'm expecting Microsoft to win the upcoming generation.
I think that you will see very little change in who adopts what next generation console. Xbox Live and Playstation Network tracks purchases, achievements and game history. Not to mention, your online friends. Unless you're already on both, these things make it less likely for someone to switch.
So what you say about Microsoft winning next gen may very well be true, but its not like Microsoft's success with Xbox 360 was because they were so awesome. They benefitted mostly from mistakes made by Sony and they only managed to dominate US marketshare while Sony still dominates the rest of the world.
If I were to bet, I'd say Steam has a good chance to win this gen for reasons I've already stated.