So... let's say that we want 20 million people to be able to use Bitcoin as P2P cash regularly (say once a day).

20.000.000 tx/day --> 232 tx/s or 13.889 tx/min --> 138.890 tx/ block

Currently txs are on average 250 bytes... but let's say that we can somehow get that down to 100 bytes... (I've see discussion on several ways of doing this).

140.000 txs x 100 bytes = 14.000.000 = 14MB


What would be the big tech constraint in 2020 preventing 14MB blocks?

Memory? Bandwidth? latency?