Some, gunslnger, live on blood. Even, I understand, the blood of young boys.
May he not be spared?
Yes.
How?
Cease, gunslinger......
I'm sworn by my fathers guns.....

I think that this needs to be seen in the larger context of Roland repeating quest. Why does it have to do specifically with Roland dropping Jake? I think he would be spared (along with others) when the cycles of Roland stop. There will be no more drawings of the boy.