Here's why that won't happen. Advertising and money. "Broadcast" by definition is inefficient and wasteful of advertising dollars. Last week's NY Times article about the death of newspapers mentioned that advertisers reach their customers via newspaper websites for $0.05 per customer compared to $1.00 per customer via dead-tree newspaper ads.
The exact same is true of television broadcast. Many ads are aired that never get look at by target eyeballs.
Think of the internet as "narrowcast." Advertising is much more targeted and efficient.
At least that's how I see it working out.
It’s already happening, the digital spectrum is being sold off, for lots of money. What’s going to happen with advertisement, what’s already happening with advertisement, is going back to the old 50s way of embedding ads right into the show. Product placements will rule the roost. You can already see the pendulum swing, not a single episode of Heroes went by without somebody getting into or out of a Nissan Versa, if you’re watching a football game on Fox you’ll get the Dodge halftime show.
Narrowcasting ads has other problems, the big one being finding your target audience. The internet hasn’t had nearly the demographic analysis done that’s already out there for print and broadcast media. Every advertiser knows who’s watching show-X, they aren’t so sure about website-Y, currently they’re using the related media to decide, they know that if show-X is drawing their target market then websites related to show-X should also, but for fully independent stuff it’s a crap shoot.