Yes, so far that is correct. I have a proposal (and coded it but since removed fro now) to allow a ledger bit to be set in data chains. So this means do not delete the older MD but keep it and create a new version. This would cost a tiny amount but as the network would keep an extra copy (i.e. the older version) then it would cost.
The idea for a ledger bit is for 2 things:
- Ledger data (so blockchain type capability if required) i.e. a data type that every update is recorded
- Individual ledger items, so even safecoin you could record and keep a transaction on the network. so for large payments, like buy a house or car then you can keep a receipt of payment and the network would always make this available.