Tree of Saviors currently has servers per SEA and NA regions. After the merge, there will be but one (per region).
For NA, Orsha will be merged into Klaipeda, and for SEA, Verena is being merged into Telsai. If you’ve got just one team on one of the servers, you’ll have no problems. But if you have teams on both servers, you might have a bit of acclimating to prepare for. The game will automatically pick which team is to be your main, and the other will become a secondary.
There’s also a new hidden class inbound, Nak Muay, which will arrive on February 20th.