Viz Media announced Blue Dragon would appear on Cartoon Network’s schedule sometime this spring. However, a handful of sources are pinpointing the start of Shu’s journey in April as part of Toonami’s 10PM-ish timeslot. Animation Insider specifically has Blue Dragon in at 10:30 PM, which means it will replace Dragon Ball Z and Bakugan Battle Brawlers will be acting as its lead in.
10:30 PM on a Saturday night? That is far from an optimal weekday afternoon time slot, but at least it's better than .hack//roots, which premiered at 5:00AM Saturday mornings.