They may not, but as long as you keep the moisture in the main soil mass OK, you should be alright.
My general procedure with layers is to disturb the new root mass as little as possible for the first year or two. I usually use sphagnum in my layers (though I'm experimenting with a more typical bonsai mix this year). I wait until the root mass is busting out of the sphagnum, then remove the layer, and pot it up in a fairly small container (a bit larger than the new root mass) using a somewhat more open soil mix...but I won't place a sphagnum ball into a pot surrounded by completely inorganic soil. I transition to the more inorganic soil over several repottings. Others may have different procedures but this seems to work pretty well for me.
Definitely good to cut back the top and shelter the tree from too much sun or wind for a couple of weeks...then gradually increase the amount of sun exposure if it seems to be doing well. Remember, the new tree is now entirely supported by a relatively small root mass compared to what it had before removal.
Good luck...