"We were hoping to debut it at E3, but we're not sure now."

The slippage appears to be due to some changes that are being made to the world map system. "For displaying characters on the world map, we were originally planning on using the method used by FF#, with a small Noctus running about on the screen. But that didn't look too great, so we ended up switching to the method used by FF#."

Those "#" signs are presumably meant to be the roman numerals of certain games in the main Final Fantasy series, but Famitsu had to block them out. Both Famitsu and Nomura agreed that the change is a major one.
Final Fantasy Versus XIII Uncertain For E3 (andriasang.com blog, 02.17.2010) <- Source

Hard to say if the world map is in danger of being replaced, but if it's a major change the world map could be affected; that would also include the airships that were planning to be in the game. It'll be nice if Versus goes with a XII style map, with a Dragon Quest VIII style overmap for the airships.