A server merger will bring a massive negative stigma, and more negative press then this game has gotten since 2 months after release. "FFXIV mergers servers after just 6 months" would be the headlines on all major sites. Good luck getting anyone else to try the game after that.

Even if it is makes the game 5-10 fold more enjoyable, it could prevent the PS3 release from being successful no matter how well they make it.

If they do a merger at this point, it would probably pay them just to shut the game down.