I don’t think there were any new proposals, and I would assume not much is going to happen in terms of implementation until after the ACME v2 API becomes available (currently scheduled for January).
You can currently somewhat mitigate this issue by either creating a new account (registration) for each certificate issuance and deactivating the account right after, or by disabling the authorizations you created after the certificate is issued. Not persisting the account key would also be good enough.
I’m not aware of any clients that operate like this or support a flag for this mode of operation. Not persisting the account key might be easy to script with some of the clients that let you provide the path to an account key combined with a RAM disk.
The Client Implementations list does contain a number of libraries in various languages, some of which support the account or authorization deactivation endpoint. Those should help if you chose to implement one of the other approaches.