I think a server merge would help all players a lot more than it would hurt them.
A lot of people would lower in rank, whales included might get bumped from the top & would have to become more competitive and probably earn Gree more money. Whales are generally the ones that think their rank means something (I’m a whale and I can assure you it doesn’t mean - if you understand the game & your toons, you can work on a specific toons that will best whales in all areas of the game).
What it means for the f2p players is that contests will be easier with more participation, finding an active guild for players in their range will be easier which means they’ll be able to work together for better rewards on temples, crypt, war etc.
It also means more engaging community for everyone (provided Gree actually did something about bullies on global & VIP but we all know reporting doesn’t do anything).
In theory merges could spark life into a dying game, but in practice this could be a distaster, who knows what kind of glitches it would cause, players might lose accounts, or maybe Gree simply just doesn’t want to put their resources towards saving the game, just get as much as they can while it dies.