It is confirmed.
QUOTE said:The player controls and some other well-received elements from MGS4 and Peace Walker have been implemented into the game. The camera from Subsistence has been adopted, as well as elements of the free roaming camera system that was implemented in MGS4 and Peace Walker.
The source is here.
Sorry if this is old news, but this addition seems good. I just hope there won't be framerate issues, cuz MGS is one of the games I'm looking forward to on the 3DS.
BTW, this game is demoed again at ComicCon (San Diego - July 21 to 24).