Sentinels of the Starry Skies looks to be the title for the localized release.
Square Enix has trademarked the title Dragon Quest IX: Sentinels of the Starry Skies in North America, after a similar trademark filing in Europe last week fueled suspicion that the game's title would be the same in both territories.
Nothing has been made official by Square Enix yet, including the fact that the game will even be released outside Japan, but it seems very likely at this point that an announcement will be coming soon.
Dragon Quest IX was released for the Nintendo DS in Japan last July, and broke sales records by selling more than 4 million copies by September.