Fair point.  I took Odalv's comment to mean that there would be no nodes except for those run by these fictitious "5 big miners."  Maybe that's not what he meant.  

Anyways, I can't see a future with less than a thousand or so nodes.  And in such a future (~one thousand nodes), I'd imagine a much larger portion of these nodes would run mining pools, simply to help pay for the node's monthly costs.  

I don't buy the "centralization" fears related to increased blocksize.