i continue to think you're focusing on the wrong metric: nodes.
That's right, a peer to peer system that derives its strength from that network model doesn't need more peers!
You actually have been focusing on a single, simplistic dynamic (as well as several over-simplified arguments, such as your nodes don't matter argument), the blocksize <> tx/s argument. It's one of the simplest of bitcoin dynamics to understand, and you seem to believe that it exists independently of all other factors. Consistent with the over-simplistic moreblocksize == moretxs that Hearn and Andresen were pushing. Fortunately, people that have real investments in the system decided that they wouldn't allow that to happen.
nodes are important. i've talked about this up the wazoo along with everyone else.
i just don't think they centralize to the degree you claim. user growth will grow node growth. also more users will grow more merchants who will host their own nodes. there is so much growth potential outside Bitcoin's small, niche community that is the current status quo.