Okay, I got my recent issue (May) of OPM and there was an article on Kojima-san as he speaks about the future of the MGS series. I'll just sum it up for you guys:
After receiving some negative feedback about MGS2, Kojima-san agreed that there were too many "passive cinematic elements" and not enough gameplay. Kojima-san also states that "Raiden was a one-time character, unlikely to return in a future installment" because he received a lot of negative feedbacks on the character's involvement with the sequel. However, Kojima-san thought that "through Raiden, we get a new perspective of Snake; a new appreciation". He talks about the missing character from MGS2, Chinaman (which MakgSnake already stated) and his abilities. Chinaman was supposed to be like a Jet-Li character with a body tattoo of a dragon. When Chinaman enters the water, the tattoo was supposed to "consume" him and changes him into a dragon. This character was supposed to possess a lot of powers and abilities that Vamp possessed (like walking on water, etc) and he was originally planned to be in the same room as Vamp when Raiden fights him. Vamp was originally supposed to be a
woman but they decided to make him a guy because of the removal of Chinaman. As for the future of MGS, Kojima-san is not sure if there'll be another game, but if there is, he won't have much involvement in it, but he'll teach his team on how to make the MGS games and hopes they'll do a good job on the rest of the series.
Well, that's it. Also, the reason why Rose in MGS2 was so buggiful, was partly influenced by Kojima-san's wife, who used to bug him about their anniversary. Of course, the guy forgot, so he thought he would incorporate this into the game. Kojima-san also said that Rose represents his "ideal" woman: Smart, pretty, and a scientist. Hmmm......

Anyway, I'm sure surprised about the Chinaman character. It would've been cool to watch his transformation from a human being to a dragon!

Hopefully, if there is going to be a third MGS, I hope his teams does an excellent job at it.