Since I composed that particular line...
Being originally a one-blog/one-install design means WordPress requires a large overhaul to the core to make multi-blog/one-install a reality (ask those who've tried). A multi-blog component has been mentioned as something desired by the devs, but that doesn't mean they're sitting around their computers right this moment coding the multi-blog edition of WordPress, even though--in a sense--they have been doing just this for at least a year, in that each new version represents a small progression towards that goal.
To quote Matt back in May of 2004:
To satisfy the hype we could say â€œthe very next version of WordPress will have full multi-blog capabilitiesâ€? and just hold off the next release until that was done, or we could continue to release progressive enhancements while multi-blog work carried on concurrently. The latter is what Iâ€™d rather do.
So, will there be a multi-blog version of WordPress? It's not risky to answer in the affirmative here. Just don't look at it so much as a specific point on the map, but as an understanding that this feature will come to be when the right elements can be worked into the landscape.