To me the issue isn't how good the new 4 strokes are,its the cost to maintain them.
My 06 WR450F has been reliable but one day it will become someone elses time bomb and most likely a parts bike.
That was never the case with a 2 stroke...seized top end...no big deal,piston,rings,a couple of gaskets,off you go.
It aint gonna get any cheaper with fuel pumps,injectors,sensors,ECU's etc etc.
I like my 4 stroke,but i love my 2 strokes....less moving parts more fun....cheaper.