If we actually end up with a forked blockchain then we will have "two Bitcoins" (or more depending upon the software being used).

What will this do?

For a start I predict it will cause all exchanges to "stop trading" (as they will not want to risk fiat losses in case they have ended up on the wrong fork).

Once the exchanges have stopped then the miners can no longer sell their BTC block rewards so that means within a very short time there will be a serious problem in the mining area.

The amount of electricity that miners are paying for is so large that they will most likely shut down their hashing operations if the exchanges have closed down which will reduce the difficulty (in two weeks).

After two weeks if the problem hasn't been worked out then everyone is basically going to walk away and the Bitcoin experiment will be declared a failure.

This is what we are facing (so you've got to wonder why Gavin wants to try and push for this).