There was a brief period of time when Ico was dirt cheap and you could find it in pretty much any bargain bin at your local Real Canadian Superstore. Sadly those days are past us now. You still might have a chance in finding it at a smaller game shop.
As far as speculation goes, here are a few thoughts:
Enemies: SOTC was a vast wasteland filled with colossi and a smattering of smaller animals. Ico occasionally pitted you against shadows. In both cases the worlds were sparsely populated. The armoured guards we see in the trailer may suggest a more populated world. At least comparatively speaking to SOTC, I'm not expecting Dynasty Warriors!
You can also see that the guards have curiously long necks, they might not be human. Their eyes look similar to the Colossi eyes, glowing.
Horns : One constant thread between ICO and SOTC is the horns. Without spoiling anything about their stories, it's enough to say that horns play an important part in both. This time around the large creature has horns, which are still growing (it's also worth noting that the creature is young, possibly a baby). In the past the horns have represented a kind of curse/redemption cycle, I wonder if that theme will continue in TLG.
The name : Seems to tie in with SOTC. Is this creature a part of the race of colossi? Will the creature eventually resemble them with stone bits of architecture?
Well that's all I can really think of for now. When I first saw the leaked footage, I couldn't get it out of my mind! I'm glad at least I can jot down some thoughts here!
Also there is some good info about the game in this 1up interview here:
http://www.1up.com/do/newsStory?cId=3174577