Are we talking war now? Between Afghanistan & Pakistan? I doubt that would happen anytime soon.
Though the border skirmishes would be very frequent as after 2014 the would be Afghans waking up from the sleep and smelling the coffee.
As a freshly re-booting nation, they would settle in the new reality at their own terms and so I am pretty sure that sparring with Pakistan is bound to happen.
But war? No. Durand line is here to stay, at least for a decade or two.
After that, we don't even know very well what would happen of Pakistan, what to say of durand ..
We cannot take the back set and we also cannot appear as colonizers in Afghanistan.
Pakistanis would lose not time in screaming Jihaad saying 'India has sided with the Tajiks and Uzbeks to wipe out the Pashtuns'.
Regards,
Virendra