Moving the ID server has nothing to do with, nor will it affect, the routes/connections/repdefs/subs already defined in your non-ID servers.
What you're *moving* between the old and new ID servers is the master list of components and 'next ids' that are used to manage the entire replication domain (ie, the contents of the 3 RSSD tables you'll be copying over to the new ID server; afterwards the contents of the old ID server will be ignored).
As for my 'NOTE' I probably should have said not to add any routes/connections/repdefs/subs/etc to any of your repservers while moving the ID server (otherwise you could end up with inconsistencies in the 3x RSSD tables).