During the Nintendo earnings briefing Q&A, Nintendo president Satoru Iwata stressed (again) that his company is making an effort to strengthen relations with third-party software developers.
Following up his point, Shinji Hatano, General Manager of the marketing division, confirmed that we’ll be seeing Dragon Quest IX in English at some point. Iwata stated at one time that Nintendo would give the Wii-exclusive Dragon Quest X marketing support in western territories, and Hatano’s latest comments indicate that the publisher will be doing the same for Dragon Quest IX.
Food for thought:
Will Dragon Quest IX receive any DSi-specific updates in time for its English release? Square could then re-release an "international edition" in Japan to squeeze a few more sales out of the game.