Satoshi did predict just that, even before he launched the network (in 2008).

    “At first, most users would run network nodes, but as the network grows beyond a certain point, it would be left more and more to specialists with server farms of specialized hardware.”   – 2008. 
    “At equilibrium size, many nodes will be server farms with one or two network nodes that feed the rest of the farm over a LAN.” – 2010.
    “The design supports letting users just be users.  The more burden it is to run a node, the fewer nodes there will be.  Those few nodes will be big server farms.  The rest will be client nodes that only do transactions and don’t generate.” – 2010.

That's a fundamental security assumption made by Nakamoto consensus. It's like assuming the discrete log problem is hard. If/when the assumption doesn't hold the security is gone.

That’s a better way of putting it. It’s a good argument for ASIC resistance and CPU dependence because it’s a lot harder to control General-Purpose CPU supply than ASIC supply.

Meanwhile my regular joe laptop can earn double its electricity cost in Monero (before it thermally locks up).

I am not a hardcore bitcoiner, but the price would fall quickly if these few controlling nodes would do something malicious. Which is against their own interest.

Probably. But a core aspect of decentralization is that you shouldn’t need to trust a few others at all.

I think it's more like limits: Trust minimization, not trust elimination.

Who cares about technicalities, the point was to let people hold the system in their own hands.

In Trust we trust!