Because gob encodings begin with type specifiers, all objects of the same type number are grouped together. That's the only guarantee made across all types.
For strings and numeric arrays, lexicographic order is maintained, yes. But be careful with structs and other types - I'm not sure about those yet, or of gob's byte ordering can be depended on.
I'm implementing for-each-of-type iteration right now, and for stringified keys, this iteration will function will be lexicographic.
