we are in similar position. boat purchased in 2008 and kept in croatian waters since then. i have written to the croatian government
several times and have just had my letters acknowledged. i have also spoken with marina owners and asked them to lobby.
if the recent push to enforce the rules regarding how long a boat and/or its owners can stay in the jurisdiction is any indication, i would not be confident that the government is thinking about the welfare of foreign boat owners.
having said that, i dont think anyone knows what will happen next year at this stage. unless they take a very liberal view on depreciated value, a decision to charge the full rate will result in a lot of boats leaving.