I think at some point in the last few years, the people developing this game kinda figured that this game wouldn't run on the PS3. So they could either scrap it or move it to the PS4. Of course the move to the PS4 meant total radiosilence until the console gets revealed. Which seems what has happened, because the game dissapeared from the face of the earth.
I think it probably was more connected with crazy ambitions of Ueda.
Last Guardian is from design game about working with AI to solve problems and this AI has fully working body physics (mentioned in one of interview).
Last time they used physic to move body was Tresspaser and that didn't end well also AI in games stopped on 2001 Black$White in which creature hardly can compare to what Last Guardian can represent in therm of game-play.
Game look incredibly complex from design perspective to me and Ueda had experience with SorC horse animations (which are still incredible) and ico AI partner. Both of them in comparison to design of The Last guardian are simply inferior.
And then there is power problem. From trailer we saw that spaces are mostly open and don't really shy from good details.
I am fan of both ICO and SotC and i can't wait for TLG. If it will be lunch title even with 599$ price tag for console i will gladly buy it. Nothing in my gaming carrier could compare to beating this collosus with sword (with dat music)
Wardevil probably won't ever come since the studio was shut down by Ignition. I could have sworn I hear that Ignition is also dealing with financial troubles too.
8 Days has been put on hold and shelved. It may come back one day. Maybe on the PS8.