4MB max in 2016, doubling at the halvings. (2MB would/could/should have been the limit at the drop to 25btc block rewards.)
Growth in the max could be halted or slowed by soft fork if alternative scaling solutions present themselves and are proven to be both functional and desired by the market.
Max Blocksize Block Reward Year(~) Native TPS(~)
1MB 50 2009 3
2MB 25 2013 6
4MB 12.5 2016 12
8MB 6.25 2019 24
16MB 3.125 2022 48
32MB 1.5625 2026 96
64MB 0.78125 2029 192
128MB 0.390625 2033 384
256MB 0.1953125 2037 768
512MB 0.09765625 2041 1536
There's something nice about the available space in a block for fee paying txs doubling at the same time the reward is cut.
If only satoshi would have spared us the drama. Doublings fight halvenings... forever.