I don't think this current model can continue as it is
but I don't think it'll suddenly die either.
It's more likely as franchises get pushed out of the picture, they are reinvented in another form.
For example, they could downsize onto mobile platforms or online games (Steam) where their residual brand power will still guarantee them enough sales to be profitable at that smaller level.
I think it'll be gradual, where the AAA continually decrease as games like Tomb Raider, Hitman, Resident Evil lose out to Call of Duty, GTA, Assassin Creed,etc. and are forced to seek another revenue model. As they find other successful ways to monetize their IPs more and more will move to that model leaving just the biggest franchises making their $100-250m games. But in the end people will tire of them and no publisher will risk making huge AAA games for new IPs when they can be more sure of profit on whatever new revenue model has been established. Whatever new model that turns out to be might ultimately turn it's biggest successes into AAA titles but those will be fewer and farther between.
Which despite what JohnLucas says, whatever model saves our beloved IPs, it won't be WiiU.
I think what Ubisoft is doing with Rayman Origins/Legends/Valiant Hearts/Child of Light/Rayman mobile games. These games are (look) great, are a ton of fun and are likely dirt cheap to make (compared to another Assassin's Creed game). They are easy to port to all platforms (even mobile) and even selling in low volumes can be profitable.
Just Dance is another Ubisoft series where they thought outside the usual AAA paradigm box and while it's massively popular could be profitable with very low sales. Maybe we'll see Prince of Persia brought back in this fashion (UbiArt framework) as well (at least on mobile/downloads).