Why may the big 6 go under and be replaced by a newcomer in less than one year

After putting my flack vest and helmet on here is why I think this may actually happen.

- Economic pressures are always working. At the moment it is the authors that bear the biggest weight. However the efficiency need will hit the agencies too sooner or later.

- Right now authors are held by the balls by the agencies whose only goal is the make money for themselves.

- In almost every other field an 30% cut will trigger an immediate revolt let alone an 80%.

- What buyers and sellers need is an efficient market. Something like the stock exchange.
They do not need an agency they need a marketplace.
The exchange  makes money by taking a small cut and operating in a very efficient and neutral way.
The exchange could operate at no cost if operated " a la google".
The exchange do not care who or what sells. His only business is to carry the transaction in  the cheapest way.
They have no business in pushing exclusivity, rewarding golds, starts or whatever. They are blind. What sells, sells.

- The reviews are dead.
We have already seen why. Yahoo pretended to control the market with human reviewers.
It was a failure. They were screwed by Google who understood that reviewing was a losing proposition
An algorithm will be devised that will make happy both submitters (with unlimited and immediate acceptance) and buyers (with meaningful searches). Chaff will be automatically pruned by sales and other criteria

- If a credible exchange appears, all authors will flock immediately to it (think about unlimited uploads and 0 commissions) starving the rest. Buyers will pay less and sellers will get more. A win-win

A final note: why this may not happen.
After all the whole market is not so big and may not attract the right  player
In this case the authors will remain in the hands of the few actual medieval barons.
It looks like authors prefer to hang separately than hang together.