And if they aren't the miners will just fork Bitcoin to a version without the coin limit. The real question is what future do the miner's choose? I see three options:

1) The new Bitcoin supply is tightly managed and the miners maintain the current deflationary pressure, ensuring a continued rise in Bitcoin's value.

2) The new Bitcoin is tightly managed, but with the aim of some modest amount of inflation akin to what most central banks aim for. In this model, transaction fees dominate mining profits since Bitcoin's value will stabilize or drop.

3) The new Bitcoin goes into hyper-inflation Weimar Republic-style, eventually becoming worthless.

I think it will be number 3. There is too much money to be made by attempting to time the inflationary spiral, and miners essentially acting as Bitcoin's central bank are in a perfect place to take advantage of it.