Hi there,
I have not posted in bitcoin talk to much, I just created this account. Does not take away the fact that I'm pretty good with money.
My view on your question:
Some pools are
very big indeed. But, as the main rule of demand and supply will apply here: the cheapest for the best will always win. So, in other words, if one really big pool would increase it's transactions fees, and would be more expensive than, lets say, the second biggest pool, the second biggest pool will draw a lot of attention and people will start moving there instead. The pool that is the biggest, and wants to profit from its size, will always have to look out for the other options that people have.
So,
all the pools must make price increases / negotiations (which is illegal in the corporate world, but of course not in bitcoin because its "free" from rules) to get the transaction fees up. But there will always be a supply - demand, so I think prices will not go up that much
The best service for the right price will win!