Lag in FFXIV was determined not by distance, but by the amazingly horrible server structure and netcode.

Yoshida already promised that the server structure of ARR will be completely redone. We'll probably see in the alpha/beta how much of this claim holds true.

From Italy (despite our internet infrastructure being crap) i never go over the 125 ping from US and Asian servers, and that's negligible latency in MMORPG. In FFXIV my lag was MUCH worse than usual.

Hopefully ARR will be on par with the rest for this. We'll see soon anyway. At Gamescom there was no noticeable lag from what I've seen, and the servers were in Japan, while the game was played from Germany.