Square Enix has filed a series of trademarks for the phrase "Sentinels of the Starry Skies" in English, French, Spanish, Italian, and German (search for trademark #008724528 on the EU trademark database to see the English application for yourself). The phrase corresponds closely to the Japanese subtitle of Dragon Quest IX, Hoshizora no Mamorubito ("Defenders of the Starry Sky").
The publisher could be waiting to get its other big RPG out the door before saying anything. It previously noted that if it does localize the DS game (which it will!) it'll be in the next fiscal year, which starts in April.