Not too bad because like FFXIII Nomura has had it in development for the past three years, so if it does come to 360 much like XIII there's no way the 360 one could launch on the PS3 version's release date in Japan. Also, even if it did gamnes like RE5 and SFIV show that Japanese gamers prefer to buy the PS3 version and games like Infinite Undiscovery, Lost Odyssey, Blue Dragon, Tales of Vesperia, The Last Remnant, and Star Ocean IV (all of which were soundly beaten in sales in Japan by Level 5's White Knight Chronicles) show that Japanese gamers don't feel motivated to pick up jrpgs on the 360 like they did jrpgs on past and present Japanese consoles.
Other than in the West, the results of Versus XIII on 360 would be quite negligible, and due to all the space for extra stuff that blu-ray affords even most Westerners would still prefer to pick up the PS3 version.