Its not that easy. A lot of complexities need to be addressed. Bringing 100% electrification on ground reality is gonna take much more time and will stop at 98%-99% only in reality owing to geographical and economic constraints.. Even after this figure is touched, a lot of other factors need to be addressed like...
1. Compensatory eloco fleet to replace diesel traction.
2. Trained electric crew to operate in newly electrified sections.
3....
more... Electric loco maintenance/production facility augmentation
Even after all this requirements are met, for emergency duty, shunting purpose and other misc tasks dloco will be required.