40k would be kind of disappointing, considering AT3 opened with over 80k. Gust should have pushed harder to make sure people knew this was another Ar Tonelico game, since even some people I know who loved the past games weren't aware at all. Although, the fact AT3 was by far the worst of the series might hurt sales. Also tying a PS3 RPG to a Vita visual novel isn't exactly the best of marketing ideas, although it makes sense story-wise.
That said, the music is amazing, as usual for Gust. Ar Nosurge is a step forward for the series from AT3, it's a lot more reminiscent of AT2, and has direct ties into AT1. I wouldn't be worried about the game financially either, since Gust has enough fans to pretty much buy out the limited editions, along with sales of CDs and other goods.