If blogging ever supplants journalism, it will be because journalism can't find a sustainable business model. Blogs cannot compete with conventional journalism on quality. Blogs are editorial spaces, and damned good ones at that, and they're useful for blowing open suppressed stories or ones that the "real" journalists couldn't find, but they have no guarantee of objectivity, no hierarchy to encourage accuracy, no attempts to at least hide biases and agendas. In fact, I'd say the biggest reason that blogs are so effective at cutting into the news' market share is either A) journalism is showing a lot of the same amateurish flaws that blogs show, or B) people are losing their trust in the mainstream media.
There's more to it, as well. The Internet, and especially gamers, are very tech-oriented. It takes a long time to clearly understand anything tech-related. Mainstream journalists, even the ones who don't just immediately decide the flavor of a story as soon as they hear it, can't expend the time needed to get the basic details right. Blogs, on the other hand, can do exactly that. A blog can cater to a niche audience, and due to the Internet's ease of distribution, can even make money doing so.
This, of course, has its own unique drawbacks, but we already know about the difficulties of growing a market into virgin, clueless demographics.