Unlike Microsoft they have strong presence in all three major regions. Unlike Nintendo they have solid 3rd party support. Both Nintendo and Microsoft have a handicap that Sony lacks. So as long as neither of them throws a curveball like the Wii, or Sony doesn't make major mistakes like with the PS3, does Sony just automatically win?

If you put it that way, basically.
However, like you said, there are exceptions in which Sony doesnt win. In fact the argument could be made that Sony was the biggest loser last Gen, losing a large chunk of its PS2 audience to both Nintendo and MS. So not always, but 3/4 wins are pretty good for a console maker.

When it comes to consoles, so far the PS3 has been the only exception to this rule. And even that will change in a couple of years time.

They don't have a strong presence in Japan anymore. 

No one has a strong presence there in terms of home consoles.

Exactly.

It hasn't even been out 6 months in Japan. The PS3 didn't have a particularly strong launch either. Let's wait and see what happens once some of the major 3rd party titles hit. 

The 360 wasn't a Sony console. But that has nothing to do with the topic anyways. 

Assuming that Sony is still around for the next generation then yeah, I think they could "automatically win".

spemanig is a broken record, he's been posting that crap for the last few weeks.