Treat it like a regular patch, just as when fortas voidas soulstones and fatecharms came out, we didnt make a new server for that .
Plenty of reasons,
People go for the 'new' and 'complete'
Example, JD Classic servers of 5 factions, only humans, veteran minority prefers this but the servers are ghost towns and it closes down. Vets only cant keep a server going, it needs its newbies.
People Migrate
A new server opens with new features and same rates and stuff, people obviously get drawn to it. The monkey franchise would be one of the first to get the server up as well, so the newbies would go there, existing MD would see large scale migration to the new server.
Voting
Ofc they may think they'll keep playing both servers, but when it comes to voting, anyone'll get the servers mixed up/ dont bother with existing MD, lose interest/ focus with all the new stuff and building brand new characters.
Split in Votes /Fall in vote rankings/Overall drop in Monkey rankings in vote sites
In the case where 'some people would like game kept the way as it is' proves true, the title explains whats going to happen. As a result, less new players get drawn in. Which is definitely not good for the server.
The economic aspect, the extra work the staff has to put in , the chaos after a brand new server(seriously , you put up with enough of this after a simple patch, imagine hundreds of people start playing the brand new server, which will obviously wont be bug proof and will be vastly untested) etc etc backs up why it should just be a normal patch.
So, just consider it a normal update, the game goes on.
Peace o.o