6. The Spanish Armada
Thanks to the likely success of the sea-based sequences of Assassin's Creed 3, there will likely be some clamour to include that sort of gameplay again in future games, and the attack of the Spanish Armada on Elizabethan England would represent the perfect opportunity to provide exactly that sort of gameplay. It might seem difficult to bring in a story that successfully knitted the naval warfare sequences with the stealth aspects of Assassin's Creed, but the various plots to overthrow Elizabeth I and replace her with Mary Queen of Scots would appear to be a good solution to the problem. Ubisoft could use the backdrop of political upheaval and the conflict between England and Spain. The protagonist could be presented as of Spanish heritage, first engaged in the Dutch Revolt of the mid-16th Century and then using the Spanish Armada attack of Britain to get onto the British Isles in order to assassinate Queen Elizabeth I. Sounds good to me.