Moreso a spiritual successor than a sequel (somewhat similar to what SoTC is to Ico). I don't want anything added to Amatersu's story, but rather, I expect they'd do something with Tsukuyomi (Japanese Moon-God) who is, according to japanese mythology, the brother of Amaterasu. But without Clover Studios, I don't think we'll see a sequel or spiritual successor anytime soon. T^T
As for the new ICO game, I hope it tells us more about the events prior to Ico, like some stuff about the Queen and how the shadows in Ico are connected to the Colossi. That's just me, though. :v
The sales were poor because people don't like to take risks. They want games they know will be good instead of trying unique and innovative games like Okami. Bah, them and their shooters.
And SoTC is a game I ocassionally still play (time trials). It defines epic - epic battles, epic scenery, epic music. Can't wait to see what Team ICO brings to the PStriple. ^_^