Is there another hard-to-predict data source that can be used in addition to timestamp?
In future we'll get rid of timestamps, we don't need them coz block height will define the timestamp (we'll have exactly 60 sec between blocks).
That means the network will treat blocks as generated right on the minute then? (In practice they won't be, due to processing lag, connection lag, etc, just that for computation purposes we regard it as exact, then try to adjust the practice to keep as close to that as possible?)