It's still possible as a ps3 title, hopefully. Then a HD re-release on ps4 in a couple of years.
If it's going straight to ps4 it will be at least until 2015 before it finally comes out.

PS4.

tgs will answer this and if it doesn ps5

Does anyone still think The Last Guardian is actually coming out? Until the announcement of Final Fantasy 15 for PS4/Xbox One, I accepted that these two games wouldn't ever see a release and if they did they've wasted so much time on them that I'm no longer interested at any price more than $20.

26% chance PS3
50% chance PS4
23% chance never
1% chance PS5

I'm almost certain the game is now a PS4 title. I can't remember where I saw it, but Yoshida was asked about it being a PS4 game and he responded with something like, "We're not ready to discuss that". That's not a sure thing but it is very curious as to why he wouldn't simply say 'no' if it wasn't. If I remember correctly, the game was supposed to release in 2010. I think that was around the time certain studios started initial development of PS4 games. I'm willing to bet the game had a lot of development issues, wasn't going to make the release timeframe, and Sony decided to scrap it as a PS3 project and move it to PS4. That would explain why we saw absolutely no new footage of the game over these last 3 years and Sony stayed very quiet about it. They probably didn't want anyone to suspect any serious developments were going on with the next platform and they had nothing to show anyways because the game was being rebuilt from the ground up. As soon as Rain and Puppeteer are done I'm pretty sure Japan Studio will go all out on getting that game done.

I would like to believe it will come out on the PS4 but if the current state of affairs continue, then this game will be forever be in "vaporware" status

I hope the project has been moved to PS4, as they seem to have struggled greatly at trying to realize it on PS3.

At this point I want it to be a PS4 game.

It would be the first stain on the crystal clear Shuhei Yoshida if the game would never come out, cause he was keeping up the hope alive by stating it's still in development , they are just not ready to show anything new, on several ocasions, even after Jack Tretton said recently that it's currently on hiatus.
But if it's not going to come out, I would just want it to be clearly stated so everyone would move on. If it will be released, it will be on PS4.
And I really, really hope, the first decision after launch of the game, would be to close Team Ico, cause this studio has been a joke for the last 8 years, keep some talent that want to ACTUALLY WORK, move them to other branch of Japan Studio, and say sayonara to the rest.