While not a definitive yes to the question, it does provide hope to Xenosaga fans, especially European fans who only got Xenosaga II. Here is a link to the Namco Bandai forum in question.
While an HD Collection of the trilogy would be nice, a release as PS2 Classics will give gamers a chance to re-live the series, or to experience it for the first time. We will keep you posted on any updates on the matter.
Source: US PlayStation Blog