There is no nuke guys! @furzerotwo have confirmed it on twitter, multiple times.
It has already been said in this thread.
Still, there’s a silver lining. It looks as though Modern Warfare 2′s controversial tactical nuke that would instantly end a multiplayer game if one player got too many consecutive kills will be removed for Modern Warfare 3. Read on for a list of the new perks and kill streaks leaked to Kotaku.