I don't think the full node count would scale as far as 12m in the growth example above, but payment channels for node services would at least reverse the decline even when it becomes necessary to support that loading.
I agree.
I've been thinking a lot about full node count lately, and I could also imagine a future where node count continues to decline but network decentralization actually improves.
Let's imagine a distant future where:
- Every major research university operates 1 full node on average (there's 108 in the US, 15 in Canada, and let's assume 150 elsewhere). That makes about 280 nodes.
- Every major bitcoin company in this "bitcoin future" and every mining pool operates a full node. Assume another 280 nodes.
- Various branches of governments in most countries run a few nodes. Assume 190 countries x 2 nodes = 380 nodes.
- And a bunch of wealthy bitcoiners operate their own nodes. Assume another 300 or so.
This gives a total of only ~1,240 nodes, but I think such a configuration would be more decentralized than the current state of the network.
I'm not suggesting that this will actually happen, just pointing out that the network doesn't necessarily need hundreds of thousands of nodes.