Formerly, there were a bunch of guidelines attached to the change of country names. Among them stuff like a maximum of letters, requirements to use Latin script, and, most famously, the required use of the countries original name in brackets if it wasn't recognisable in the new name, with varying standards of precision.
These guidelines will be mostly gone. From 19th December on, there is no limit on characters (provided there is no limit somewhere in the code, which we don't yet know of), and you can use whatever script you like, provided it can be reproduced by other browsers without having to install something. Which basically means that you can use every script already used in RL, but you can't make up a new one (as in, make a new font, and use that), because nobody else would be able to see it.
The names in brackets will also be gone. The original country names will still be recorded, and deviation from these names still need a good reason, but in all the cases where they are just declinated or written in other languages than English, the brackets can be gone. There will be a new thread in the moderation forum listing the original names, so they can still be found by players. And that, in turn, means that over time, new "original" names can be developed (as has happened in the past, most recently, to my knowledge, with Athlorcaea for Hutori). However, if you want the brackets gone from the names as they are now, you have to do this by using the normal renaming procedure (2/3rd majority in a bill that clearly states the proposed name change), they will not be deleted automatically.