So, I always find several implied assumptions when it comes to scaling.

1) That everyone on the planet is going to be using crypto.

+won't be a black/gray market niche

2) That everyone on the planet will use a *single* crypto.

+won't be a range of different cryptos that provide differing utility

3) That it can't scale given a slow enough rate of adoption.

+consumer tech advances (Moore's law)

+protocol scalability improvement (Monero tx size shrinking by 80% since inception)

4) That decentralization is binary and not a spectrum.

+otherwise why not 0.1MB blocks instead of 4MB? It's unlikely and seems pretty convenient the 4MB blocksize just so happens to be the "cut off" point for being considered decentralized.