There are plans to extend this line to a line being built by Iran to the Afghan border near Herat. There might be a branch to Turkmenistan. Northern Afghanistan is relatively stable, so this line is realistic.
In addition, the Chinese may finance a line from Mazar-i-Sherif to Kabul that would continue on to Jalalabad and the border with Pakistan. This line would have to go through area where there is fighting which reduces the likelihood of its ever being built. However, if the Chinese provide grants )like for the line that is being built to Mazar-i-Sherif) construction might inject enough money into the local economy to create stability.