Pools are masters, and miners are slaves. Yes, miners can change their masters, but they can't get free. In the end, the pools that give the most (more income due to natural reasons) will attract most miners.
Just imagine an extreme situation with ~8Gb (read: very large) blocks. In this case, apparently the most effective configuration would be 1 single pool, or a couple pools located in the same data-center. And you miners wouldn't be able to do anything with this centralization.
Hogwash. Anyone with sufficient capital can afford to solo mine, even today. For a few thousand dollar investment one can purchase miners that will score a block in under two years, on the average. The risk involved is that this won't happen and one will lose their investment, but if they are not poor and living in their parent's basement this will not be much of a problem. Other people may even consider this situation beneficial, if they consider it a form of gambling.
As to the single data center idea. I suggest you do the math. There are two costs here, the node cost and the orphan cost. To get the total node cost, calculate the cost of running a single node and multiply it by the number of pools. The node costs consist of storage cost, processing cost, and bandwidth cost. These all relate to the number of transactions the network processes, so you can calculate a node cost per transaction. (You can look at prices quoted by Amazon AWS, etc.) Now multiply this cost by the number of pools. I think you will find that there can be quite a large number of nodes that can easily be supported by existing transaction fees, far more than the number of pools of significance today.
The orphan cost can also be estimated, but it depends on the protocol design and network topology between the pools. The question of one data center vs. multiple data centers comes down to the speed of propagation. The speed of light can not be avoided, but the block size need not affect the results significantly provided an efficient protocol is used. There is no need to "store, verify and then forward" blocks, but even if this is done the orphan rate will still be low with 4 GB blocks if the data centers are connected by 10 Gbps pipes and the number of hops is kept low. Much better designs are possible, as would be known to any networking expert or even bittorrent user.
I do not expect to convince any small blocker, which is why I am not putting out any numbers (a.k.a. targets). Rather, I hope that some fence sitters might do their own calculations and reach their own conclusions. My conclusion is that some work is needed before there can be a large increase in network transaction capacity, but this mostly involves improvements in the bitcoin network protocols and in the processing efficiency of the network hardware.