What about bandwidth? I believe Bitcoin’s bandwidth needs, as a decentralized network, is very underestimated. Rate of growth for bandwidth is slow, and network latency slower, which means that block propagation speeds might not scale at the same rate if average bandwidth among nodes increases.
If block size limit isn't changed, that means bandwidth/latency requirement won't changed much while bandwidth/latency is slowly growing, which means bandwidth/latency problem won't make Bitcoin less decentralized over time.