As one of my multiple less than interesting to most people's interests has been to follow the history of videogames.  What I have seen, historically, is that the videogame business is cutthroat and console brands lose dominance.  In every generation, people expect a name to remain around forever, but fails.  Look at this history:

1. Back in the 70s to early 80s (pre-videogame crash), Atari was the name.  The Atari Mount Fuji symbol was even on a building in the movie Bladerunner (well, rumor has it that).  Atari fades.

2. Post crash, Nintendo was the king, and the name in videogames.  The NES rules.  Atari goes to failed competitor with first the 7800, then the Lynx, and then the Jaguar.

3. Sega challenges Nintendo, and loses the lead, and then becomes an also ran like Atari.  They had the Master System which failed, then some success with the Mega-Drive/Genesis, and then go niche and drop out with Dreamcast.  They are now a marginal third-party developer who has a mascot that has gone onto long-past expired.  While Nintendo makes a comeback of sorts, it falls behind...

4. Sony releases the Playstation console, spawned from a failed partnership with Nintendo.  Easy to design for, and a polygon  powerhouse, and third-party friendly, it goes on to dominate.  It then manages to come out with the PS2, which then is the end of Sega as a console maker.  

5. Now we are here now.  Nintendo comes back, out of nowhere with the Wii, and changes the game.  Microsoft, entering prior generation, surpasses Sony around the world, and Sony becomes third in console sales.  The pattern continues.

So, given this historic cycle, how can anyone say there is strong ties to a given brand for consoles?  Like, why is the Playstation name, expected to be pure magic?  The Playstation name as a portable, failed to surpass the Nintendo DS, which is technical inferior.  Like, if Atari or Sega returned to the console business, would anyone care?

In the absense of any strong reason to choose one platform over another brand becomes a very important factor ... You can see this in the previous generation where the differences between the Dreamcast, PS2, Gamecube and XBox were all fairly minor, and many people who were entirely happy with the experience they had with the Playstation favoured the PS2.

Why people believe that brand will become important for the PS3 is because they need some sort of a justification for their unrealistic belief that the PS3 can see massive sales later in its life.

What has been seen historically is that console makers get trapped by their own success. The top dog will often remain attached to a prior generation console far too long, and their competition is able to beat them by focusing on just one given generation offering. This is what took Sega down, too many offerings. Now you have Sony still tied to the PS2, unable to just drop production, because the PS3 no longer plays PS2 games. Sony handled the transition from Playstation to the PS2 better than anyone else. Whether or not Sony can do with the PS3 what Nintendo did with the the SNES and come back to beat their competition in total sales, remains to be seen.