I can understand how needing greater bandwidth can cut off a minority of miners.. but how can it concentrate it into the hands off just the few? If you look at bandwidth usage statistics aren't a majority of the people that mine bitcoin currently considered high bandwidth already? Therefore this "centralization" simply means into the hands of what already is a majority which should theoretically get even more dispersed the more high bandwidth connections are available right? Or is some extremely powerful bandwidth connection able to eliminate "normal" high bandwidth users?
What makes you think miners are "high bandwidth"? Pools tend to have reasonable amounts of bandwidth, if only to resist DDoS attacks, but the pools aren't the issue, validation is. P2Pool is currently the best example, because every miner participating in P2Pool runs their own fully validating node that ensures the blocks produced follow the Bitcoin rules. With the getblocktemplate and stratum mining protocols, again miners know what blocks they are actually mining and can fully validate them to ensure the rules of Bitcoin are followed.
Relay nodes matter too. Because running a fully validating node is very cheap, there are lots and lots of relays out there. A core principle behind Bitcoin's security is that information is easy to copy, and hard to censor, which means that the large number of relays protect you because it's very likely you'll connect to an honest relay and you'll get an honest, uncensored view of what is happening on the network.
So your biggest fear is that alternative solutions to the block size limit won't be made? In other words what the other guy mentioned bitcoin clearing houses? How does that help decentralization?
You don't need to trust clearing houses and other payment services built on top of Bitcoin if you can run a fully validating node. The protocols by which those payment services operate can be written in such a way that everything they do, every single transaction, is auditable, and critically, if they commit any fraud, you'll be able to prove that fraud. You publish your proof of fraud on a P2P network, it'll get broadcast to everyone on the network in seconds, and the payment services business will collapse immediately. I've written about these concepts multiple times; I'll post a big summary of the options later tonight.
On the other hand, if you can't run a fully validating node, you can't monitor the on-chain activities of those clearing houses to make sure they really are still holding the funds they claim they do. You have to take their word for it. At the same time, if you can't fully validate blocks, what's to stop miners and the few remaining validating nodes from getting together and creating blocks that collect fees from transactions that don't exist, thus inflating the money supply?