Yamaha just introduced their concept of the way forward in engines with a crossplane 3 cylinder engine. Like the engine in the current R1, the crossplane configuration delivers smooth application of power with a distinctive, and most would say, very satisfying exhaust note.
As a 3 cylinder, they open the way to new, smaller displacement motorcycles, though no mention of what displacements might be in the offing were made. The engines are lighter and more compact than the current inline fours so a whole new small and mid range series of bikes is possible.
The introduction was long on generalities and short on specifics, so where they'll take this is open to speculation, which is sure to be plentiful. I hope we'll see it deployed soon.