As it stands, the idea is to only introduce this one change in the hardfork. It's possible that someone else may want to introduce a separate change, but combining such changes, especially from two different development groups increases the testing challenges. As far as I know, the only other development group making major changes to Steem code right now is Steemit. I believe their next planned change is implementation of rocksdb, which shouldn't require a hardfork.
I haven't heard of anyone discussing a change to sign up that requires a hardfork, but such a discussion may be going on somewhere.