Could you tell us how would you determine what the block size limit should be in the future?
Estimate the time it takes for blocks to be propagated through the majority of the network. Determine the block size that still takes a reasonable amount of time to propagate through the network and use that as the max block size.
Currently, the 4vMB blocks have a median propagation time of 6.5s (or less since the study was done a long time ago). If we can keep the expected stale rates to be <5%, then I consider it an acceptable compromise. Expected stale rate is a function of the time it takes for the block to propagate and the block intervals.
1. It is worth noting that the speed of distribution of blocks in general on the network does not play a special role for mining. The main thing is what is the speed of distribution of blocks within the subnet that covers miners. If the speed inside the subnet was at the level of 1 second, we would have ~1.6% of orphan blocks. But there are much fewer orphan blocks at the moment. Somewhere on the forum, a figure of 0.0024% was given (I can't vouch for the accuracy). This means that the speed is now much less than 1 sec.
2. When using a technology such as spv mining, the block size ceases to affect the number of orphan blocks. Miners start mining the next block almost immediately after the block appears. However, this increases the number of empty blocks. But I think this is quite a reasonable compromise: reducing the number of orphan blocks at the expense of some increase in empty blocks. Moreover, an empty block, which sometimes appears a few seconds after a non-empty block, does not cause any inconvenience to users.
From all this, we can conclude that, for example, 10 MB. blocks do not pose any threat to network security from orphan-blocks.