When roots get to bottom of container early, what happens to the plant?

Details,

I planted a Red Sails Lettuce plant 16 oz Kirkland water bottles. Three 3/16 wicks travel from the middle of the container out the bottom of the bottle. Plants lap up the water in a black catch tray under an indoor OTT grow light. After 2 weeks, the plant is 2" tall and starting its 2nd set of leaves. But I see the roots reaching almost to the bottom of this 6" tall 34 cubic inch container!

A. Is this normal for lettuce?

B. If lettuce becomes root bound a few months from now, will it still bear OK?