Aye, one of the first announcements about KL2 was that it will have online co-op. I think everyone will agree that releasing a game today that is obviously heavy on co-op and only being split-screen in this day and age just wouldn't work.
Speaking of the N64, I still would love to try out Goldeneye64 today and see if it still holds up in 4 player split screen as well as it did back then. Some of my most intense multiplayer memories come from Bunker with mines only, oh the humanity!
Anyway, yeah, KL2 is online and offline co-op
Get Perfect Dark XBL and gather up 4 friends to splitscreen action. Awesome