I'm not really sure and I need some confirmation.

PC/PS3/360

Did this really need another thread?

Rumors say it's also on the PS3 and PC

http://dlb-network.com/2009/06/many-kojima-titles-in-the-works-to-be-shown-at-e3/

First, most of us now know that a new title, Metal Gear Solid Rising is coming to the 360, PS3, and PC but there is still no release date.

There is now speculation that a Metal Gear game could hit the PSP in 2010. GamePress lists the game to be called Metal Gear Solid: Peace Walker, expect this one to be announced at Sony’s press conference tomorrow, June 2nd.

it’s speculated that Konami may give the Castlevania franchise to Kojima Productions and they will have the roll of working on the newest game in the franchise, Castlevania: Lords of Shadows

This is a lot of stuff, get ready to hear more announcements by Kojima Productions as E3 progresses.
rk.com/2009/06/many-kojima-titles-in-the-works-to-be-shown-at-e3/

No it's on the PC and PS3

PC/PS3/360

and not done by kojima or his team (from what i heard.......... not sure)

I still haven't seen any good confirmation that it isn't exclusive to 360.

I have heard some people say some PR person said it would be multiplat, and that person above me a few posts provided a crappy source since that source didn't back up their claim with any source/knowledge.

I'm sure it very likely will be multiplat, but I haven't seen any solid evidence of that yet.

Confirmed PS360 + PC multiplat.

i dont think its exclusive and i dont think its will come to the PC.

Still waiting on some actual confirmation other than people saying "Confirmed 360 + PS3 + PC"