Is Ignorance Bliss?
Four strokes seem to be dominating all "small" gas power sources that used to be 2 stroke by default. This isn't only true for bikes, of course; there are even 4 stroke weed eaters.
But there is a fatal flaw to the argument that 4-strokes will ULTIMATELY phase out the 2's. Why you ask? I remember reading a fascinating article in a '92 - '94 issue of Popular Science about "new, very efficient yet low emission 2-strokes" being tested in cars
. They weren't your typical lawn trimmer or bike engine. They had an independent oil/lube system, some were water cooled, but the majority being tried in cars were 1.6L to 3.0L 2-strokes that not only made the cars very light and nimble w/air cooling, but efficient and practical too. (Forget about performance, these cars did 0-60 between 4-6 sec.)
The enthusiasm waned almost overnight for this new breed of two stroke. Why? Engineers seemed to have given up. Two strokes can be pollution dumping, unpredictable, unreliable machines when cheap is the key word for max power. But with better computer tech (if new cars have computers precisely controlling valve timing in their 4-stroke engines, why can't computers control port timing and envelope through a range of RPMs in 2-strokes) I think a new breed of quiet, predictable, reliable, low emission 2-strokes could be on the horizon that could smoke any 4-stroke, no matter how fancy.
It just takes consumer demand OR some madman with a vision and time/money (not I) to make a new breed of small, insanely powerful bikes.