toyota's and honda's biggest technical breakthroughs have been in petrol engines.they still havent reached their peak as yet.by bringing in diesel engines they will sell more cars but also as a sideproduct,their petrol engines will die a slow death.
they cannot let go of vtec's and vvti-i's so soon.
look what happened to the skoda 1.8tpi.it's a brilliant engine but just because skoda has the 1.9tdi,the petrol cars dont sell .
the diesel industry is still in its infant stage atleast in india(considering the technology),its going to take atleast another 5years till all the major players capitalize on the diesel market and then honda and toota will begin their onslaught.so wait and earn for 5 more yrs