Lelouch will not conquer Area 11 until episode 23.

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Area 11 is the hardest colony of Britannia to overthrow because it's the empire's primary source of Sakuradite. The Emperor would sooner sacrifice Schneizel than allow Lelouch to take it over; if the Sakuradite ceases to flow, Britannia's war machines falters because all Knightmare Frames need Sakuradite to operate. The Vincent models will halt indefintely since they use so much more Sakuradite than the Gloucasters and Sutherlands, meaning that once Lelouch conquers Area 11, Britannia will be on the defensive, especially if Schneizel is dead.

SInce Geass is supposed to end at episode 23, I don't think Lelouch is going to take over Japan until that time for these reasons. It's episode 7 and he hasn't made much progress beyond where he was in the first season, and there will be a detour into China in the upcoming episodes.