I believe so.
The plugin doesn’t let you change a field’s meta key when editing it. This is a protection mechanism so you don’t inadvertently end up with orphaned data.
So if you need to change a field’s type, you have to delete the field in the WP-Members Fields tab and recreate a new field with the same meta key.
Deleting the field in the fields tab doesn’t delete any existing user data. It just removes the field from the field list.
As long as the new field’s meta key matches the original, the user data will match up.
Keep in mind this doesn’t necessarily hash the data in the database, since all custom user fields are user meta, and user meta fields in WP are all text. If you need them hashed, that’s a different story.
Also, you may need to test out just how well the password field works for this application before using it in this manner just to make sure you don’t inadvertently blank user data. The password field type option was originally in there for customizing the WP password and confirm password fields. The confirm doesn’t get saved, so I haven’t done much testing for using this field type with user meta fields. I’d say test it first and check that updating profile data aside from the password doesn’t blank the field for the user before you make a wholesale change.
Side note for other field types – if the field is a type that puts in specific data, such as checkbox, select, etc, then you have to make sure that the replacement field’s data options work with the existing user data. For example, if changing from text to select, any text entries that doesn’t match the select field’s options will show as empty even though there is data in the field. That’s of course not the same going the other direction – such as going from select to text, since there is no data constraint. But none of that really applies when changing text to password.
