Honestly I'd prefer they not merge all three the servers lag enough with just single servers, nem+tranq shouldn't be too bad considering how few players there are on tranq but if you make all 3 merge its going to be bad unless aeria updates their servers.
merging all 3 might:
1) force Aeria to update their servers, or
ii) cause there to be so much lag/confusion/problems that everyone quits and ends their current misery early, or
c) everything goes smoothly and everyone is happy.
i don't see the point of merging just nemesis and tranquility. that's like adding 5 people to nemesis.